Venn diagram of two groups
In a class some children like cricket, some like kabaddi and some like both. To show such overlapping groups we draw two circles that overlap.
Venn diagram : one circle for each group. The middle part of two circles holds those who are in both groups. The part outside the circles holds those who are in none.
Parts of the figure
| Part | Meaning |
|---|---|
| only A | in the first group only |
| middle | in both groups |
| only B | in the second group only |
| outside | in no group |
Each part of the figure has its own number; it is the number of children in that part.
- e.g. only A : 8.
Total in A = only A + the middle part.
- e.g. 8 + 6 = 14.
A or B (or both) = only A + middle + only B.
- e.g. 8 + 6 + 5 = 19.
All the children = all parts in the circles + the number outside.
- e.g. 19 + 3 = 22.
circle A = children who like kabaddi, circle B = children who like drawing. How many children like only kabaddi?
- Look at the part of A only.
- Answer : 9.
circle A = children who like kho-kho, circle B = children who like cricket. How many children like kho-kho in all?
- A only + the middle : 3 + 3.
- Answer : 6.
circle A = children who like kho-kho, circle B = children who like cricket. How many children like kho-kho or cricket (or both)?
- Add the three parts : 11 + 7 + 10.
- Answer : 28.
Read each part separately; the middle number is counted in both circles.
Forgetting the middle number when finding the total of A.
Memory clue : "A circle is a house; the middle is the house shared by both."
"or" means add; "both" means the middle number; "neither" means the outside number.
Spot the difference
| Word | Which number |
|---|---|
| only A | the part of A only |
| A in all | only A + middle |
| both | the middle part |
Practice questions
- 1 circle A = children who like cricket, circle B = children who like kho-kho. How many children like only cricket?
- 2 circle A = children who like kabaddi, circle B = children who like cricket. How many children like kabaddi in all?
- 3 circle A = children who like cricket, circle B = children who like singing. How many children like both?
- 4 circle A = children who like singing, circle B = children who like kabaddi. How many children like singing or kabaddi (or both)?
- 5 circle A = children who like kabaddi, circle B = children who like singing. How many children like neither?
- 6 circle A = children who like drawing, circle B = children who like singing. How many children are there in all?
- 7 circle A = children who like reading, circle B = children who like kabaddi. How many children like exactly one game?
- 8 circle A = children who like singing, circle B = children who like kabaddi. How many children like singing in all?
Show answers (try them yourself first)
- 110
- 215
- 33
- 417
- 57
- 629
- 711
- 815
Adding, subtracting and the sums on "both"
A class has 30 children; 18 like tea and 15 like milk. 18 + 15 = 33 but there are only 30 children! It means some children were counted in both.
When you add two groups those who are in both are counted twice. So total = first group + second group − both.
Words and operations
| Word | Operation |
|---|---|
| or | add, middle number once |
| and / both | the middle number |
| only | subtract the middle number |
| none | subtract from the total |
Add the two groups and subtract the number of both once.
- e.g. 18 + 15 − 5 = 28.
The difference between the total and "those who like at least one" is those who like neither.
- e.g. 30 − 28 = 2.
To find those in only one group subtract both from that group.
- e.g. 18 − 5 = 13 only tea.
When you get the answer add all the parts and match with the total.
- e.g. 13 + 5 + 10 + 2 = 30.
A class has 22 children. 7 like kabaddi and 10 like singing. 3 like both. How many like only kabaddi?
- 7 − 3 = 4.
- Answer : 4.
A class has 21 children. 8 like cricket and 12 like reading. 4 like both. How many like neither?
- Those who like at least one : 8 + 12 − 4 = 16.
- Those who like neither : 21 − 16 = 5.
- Answer : 5.
A class has 31 children. 18 like kabaddi and 12 like singing. 8 like neither. How many like both?
- Those who like at least one : 31 − 8 = 23.
- Both : 18 + 12 − 23 = 7.
- Answer : 7.
After adding two groups subtract the number in both once.
Not subtracting the number in both; it is counted twice.
Memory clue : "Added twice, subtract once."
First draw the circles and fill all the parts; then read off the answer.
Spot the difference
| Question | Operation |
|---|---|
| likes both | A + B − (at least one) |
| only A | A − both |
| neither | total − (at least one) |
Practice questions
- 1A class has 29 children. 18 like kabaddi and 16 like drawing. 9 like both. How many like only kabaddi?
- 2A class has 27 children. 12 like kabaddi and 21 like reading. 9 like both. How many like only reading?
- 3A class has 28 children. 9 like kho-kho and 18 like cricket. 6 like both. How many like neither?
- 4A class has 25 children. 17 like reading and 10 like drawing. 3 like neither. How many like both?
- 5A class has 23 children. 15 like drawing and 16 like cricket. 9 like both. How many like neither?
- 6A class has 20 children. 8 like reading and 11 like kabaddi. 3 like neither. How many like both?
- 7A class has 21 children. 12 like reading and 12 like drawing. 5 like both. How many like only reading?
- 8A class has 31 children. 15 like cricket and 16 like kabaddi. 4 like both. How many like neither?
Show answers (try them yourself first)
- 19
- 212
- 37
- 45
- 51
- 62
- 77
- 84
Venn diagram of three groups
Cricket, kabaddi and kho-kho : some children play all three, some only two and some only one. When three circles overlap seven parts are formed.
The three circles make seven parts : only A, only B, only C, common to A and B, common to A and C, common to B and C, and common to all three. The eighth part is outside the circles.
Seven parts
| Part | Of how many |
|---|---|
| only A, B or C | of one only |
| AB, AC, BC (without the third) | of two |
| the middle | of all three |
Total of one circle = all four parts inside that circle.
- e.g. A : only A + AB + AC + all three.
"Exactly one" = only A + only B + only C.
- e.g. 5 + 4 + 6 = 15.
"Exactly two" = AB + AC + BC (do not take the middle).
- e.g. 3 + 2 + 4 = 9.
"At least one" = the sum of all seven parts; the outside part is separate.
- e.g. 5 + 4 + 6 + 3 + 2 + 4 + 1 = 25.
circle A = children who like kabaddi, circle B = children who like cricket, circle C = children who like drawing. How many children like only kabaddi?
- The part of A only.
- Answer : 6.
circle A = children who like singing, circle B = children who like kho-kho, circle C = children who like cricket. How many children like singing in all?
- All four parts of A : 4 + 7 + 7 + 2.
- Answer : 20.
circle A = children who like drawing, circle B = children who like kho-kho, circle C = children who like kabaddi. How many children like exactly two games?
- Leave out the middle of all three : 5 + 7 + 1.
- Answer : 13.
Seven parts in three circles; decide which parts to take from the words of the question.
Taking the middle part (all three) in "exactly two".
Memory clue : "Only : one, two, three — count the parts."
When you take a circle run your finger over its four parts and add them; none is missed.
Spot the difference
| Word | Parts |
|---|---|
| exactly one | only A + B + C |
| exactly two | AB + AC + BC |
| all three | the middle |
Practice questions
- 1 circle A = children who like kabaddi, circle B = children who like cricket, circle C = children who like drawing. How many children like only kabaddi?
- 2 circle A = children who like kabaddi, circle B = children who like drawing, circle C = children who like singing. How many children like all three?
- 3 circle A = children who like kho-kho, circle B = children who like kabaddi, circle C = children who like cricket. How many children like none of the games?
- 4 circle A = children who like singing, circle B = children who like kabaddi, circle C = children who like reading. How many children like singing in all?
- 5 circle A = children who like kho-kho, circle B = children who like reading, circle C = children who like cricket. How many children like exactly one game?
- 6 circle A = children who like cricket, circle B = children who like singing, circle C = children who like kho-kho. How many children like at least one game?
- 7 circle A = children who like kho-kho, circle B = children who like drawing, circle C = children who like kabaddi. How many children like exactly two games?
- 8 circle A = children who like singing, circle B = children who like kabaddi, circle C = children who like reading. How many children are there in all?
Show answers (try them yourself first)
- 15
- 22
- 34
- 422
- 513
- 630
- 713
- 840
Choosing the right figure for a relation
To show animal, cow and tiger in one figure the cow and the tiger sit inside the big circle of animals, but apart from each other.
Three groups can be related in a few ways : one inside another, two separate ones inside one big one, all three separate, or all three overlapping. Spot the relation when you choose the figure among the options.
Kinds of relation
| Figure | Relation |
|---|---|
| figure 1 | one inside another (fruit, mango, Alphonso) |
| figure 2 | two separate ones inside one big one (animal, cow, tiger) |
| figure 3 | all three separate (cow, pen, river) |
| figure 4 | all three overlapping (doctor, teacher, player) |
First compare the groups two at a time : does one fall inside the other, are they apart, or do they share something.
- e.g. cow and animal : the cow is among animals.
If one group falls wholly inside another the small circle is drawn inside the big one.
- e.g. a mango is among fruits.
If two groups can share something their circles overlap.
- e.g. a doctor can also be a teacher.
When all three pairs are settled choose the figure with the same relations.
- e.g. three separate : three separate circles.
Which figure shows the relation among Vehicle, Four-wheeler, Car?
- a car is a four-wheeler and a four-wheeler is a vehicle.
- Answer : 4.
Which figure shows the relation among Animal, Cow, Tiger?
- cow and tiger are both animals but different from each other.
- Answer : 2.
Which figure shows the relation among Men, Women, Doctor?
- men and women are separate; doctors can be in both.
- Answer : 4.
Compare two groups at a time to settle the relation; then choose the three-circle figure.
Showing men and women as overlapping; they are separate.
Memory clue : "If it falls inside draw it inside; if apart draw it apart; if it mixes let it overlap."
Look at the group that sits between two groups; if it mixes with both its circle spreads over both.
Spot the difference
| Groups | Figure |
|---|---|
| fruit, mango, Alphonso | one inside another |
| animal, cow, tiger | two separate inside a big one |
| men, women, doctor | two separate + one over both |
Practice questions
- 1 Which figure shows the relation among India, Maharashtra, Pune?
- 2 Which figure shows the relation among Sun, Table, Fish?
- 3 Which figure shows the relation among Game, Cricket, Kabaddi?
- 4 Which figure shows the relation among Student, Player, Singer?
- 5 Which figure shows the relation among Men, Women, Doctor?
- 6 Which figure shows the relation among Fruit, Mango, Alphonso?
- 7 Which figure shows the relation among Doctor, Teacher, Player?
- 8 Which figure shows the relation among Boys, Girls, Player?
Show answers (try them yourself first)
- 13 (Pune is in Maharashtra and Maharashtra is in India).
- 23 (three different things).
- 33 (cricket and kabaddi are games but different).
- 44 (a student can also be a player and a singer).
- 51 (men and women are separate; doctors can be in both).
- 64 (Alphonso is a kind of mango and mango is a fruit).
- 72 (one person can be a doctor, a teacher and a player; the groups share members).
- 81 (boys and girls are separate; players can be in both).
Mixed questions and exam tricks
In the exam sometimes a figure is given and sometimes the question is in words. First draw or read the figure, then pick exactly the right parts and calculate.
Three steps : (1) draw or read the figure, (2) pick the parts from the words of the question, (3) add or subtract and match with the total.
Three steps
| Step | Job |
|---|---|
| 1 | draw or read the figure |
| 2 | pick the parts from the words |
| 3 | add or subtract and match |
If there is no figure draw two circles and fill every part.
- e.g. total 40, both 6 : the middle part is 6.
When the question says "only" subtract the middle part.
- e.g. A = 20, both = 6 : only A = 14.
Add all parts and match with the total children.
- e.g. 14 + 6 + only B + outside = 40.
With three groups lay out the seven parts and fill them starting from the middle.
- e.g. all three first, then two at a time, then one at a time.
circle A = children who like singing, circle B = children who like kho-kho. How many children like neither?
- The number outside the circles.
- Answer : 4.
A class has 18 children. 8 like cricket and 13 like drawing. 4 like both. How many like only drawing?
- 13 − 4 = 9.
- Answer : 9.
circle A = children who like kabaddi, circle B = children who like kho-kho, circle C = children who like reading. How many children like at least one game?
- Add all seven parts inside the circles.
- Answer : 33.
Three steps : figure, pick the parts, calculate; match the sum at the end.
Calculating in the head without drawing the figure.
Memory clue : "First the circles, then the numbers."
In a three-group question fill the middle first; the other parts follow from it.
Spot the difference
| Question | Operation |
|---|---|
| at least one | add all parts |
| exactly one | add the only-parts |
| none | the outside number |
Practice questions
- 1 circle A = children who like singing, circle B = children who like kho-kho. How many children are there in all?
- 2A class has 24 children. 14 like drawing and 13 like kho-kho. 8 like both. How many like neither?
- 3 circle A = children who like kabaddi, circle B = children who like kho-kho, circle C = children who like drawing. How many children like kabaddi and kho-kho but not drawing?
- 4 circle A = children who like reading, circle B = children who like singing. How many children like exactly one game?
- 5A class has 26 children. 15 like drawing and 8 like singing. 7 like neither. How many like both?
- 6 circle A = children who like kabaddi, circle B = children who like kho-kho, circle C = children who like cricket. How many children like exactly one game?
- 7 circle A = children who like drawing, circle B = children who like kho-kho, circle C = children who like cricket. How many children are there in all?
- 8 Which figure shows the relation among Animal, Bird, Sparrow?
Show answers (try them yourself first)
- 132
- 25
- 35
- 414
- 54
- 613
- 735
- 83 (a sparrow is a bird and a bird is an animal).
Quick revision of the whole lesson
| Topic | Memory clue |
|---|---|
| Two groups | or : add; both : the middle; only : subtract the middle |
| Sum | Added twice, subtract once |
| Three groups | seven parts; the middle first |
| Relation | inside, apart or overlapping |
🎯 Most important points for the exam
- Total = first group + second group − both.
- "Only" means subtract the middle part.
- Three circles have seven parts; the outside part is separate.
- Do not take the middle part of all three in "exactly two".
- To settle a relation compare the groups two at a time.
- Add all parts and match with the total.
"First the circles, then the numbers; subtract both once."