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Review: Part 1 topics, Venn diagram
Textbook: Part 1, pp. 84–85
GoalReview the topics of Part 1; counting with a Venn diagram.
New words
Venn diagram · Venn diagrammasicommon (shared) · umumiytechnology · texnologiyacounting twice · ikki marta sanash
Explanation
In a Venn diagram the place where two circles overlap shows what belongs to both groups. To find the total we count the shared part only once: only-first + shared + only-second. In this lesson we also review adding, subtracting and equations.
Worked examples
Only football 8, both 4, only chess 5: total 8 + 4 + 5 = 17 children.
(2 + 6) + (6 + 4) = 18 is wrong, because the shared 6 was counted twice. Correct: 2 + 6 + 4 = 12.
Class activity
“Two hoops”: two hoops overlap on the floor. Children choose their place by “I like football”, “I like chess”; those who like both stand in the middle. The class counts each part and the total.
Practice
1
Only football 8, both 4, only chess 5. How many children in all?
17
2
14 children like football and 6 of them also like chess. How many like only football?
8
3
56 + 34 = ?
90
4
93 − 21 = ?
72