Sets
Union, intersection, Venn diagrams and counting subsets.
Learn with Kutty
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A set is a group of things. Circles that overlap show what groups share.
Look: A class of 40: 15 only cricket, 10 both, 8 only football, 7 neither.
✏️ Your turn!
Type your answer and press Check. Kutty will tell you if it is right.
1A = {1, 2, 3}, B = {3, 4}. What do they share?
212 in A, 9 in B, 4 in both. In A or B?
3How many subsets does {a, b} have?
! Careful!
✗25 + 18 = 43 play a game (more than the class!).
✓Take away the overlap: 33.
✗Writing 25 in the cricket-only part.
✓Start in the middle: only cricket = 25 − 10 = 15.
See the whole lesson on one page
A set is a group of things. Circles that overlap show what groups share.
To count everyone in either group, add the two groups, then take away the overlap once, because those children were counted twice.
Think of it like thisSome children play cricket, some play football, and some play both. The children who play both stand in the overlap.
- ∪ (union)
- In either group.
- ∩ (intersection)
- In both groups.
Solved together
In a class of 40, 25 play cricket, 18 play football and 10 play both. How many play neither?
Children who play at least one: add, then remove the double-count.
25 + 18 − 10 = 33Everyone else plays neither.
40 − 33 = 7
Answer7 children play neither.
Now practise it
Kanakku makes new questions on sets every time. It shows the working and gives a hint when you are stuck.