40
A property of comparison
Textbook Part 1, pp. 82–83
GoalCompare sums without calculating: if one addend is the same, compare the other.
New words
without calculating · hisoblamasdanthe same · bir xilthe letter a (any number) · a harfi
Explanation
Because 6 > 3, we know 4 + 6 > 4 + 3. Both sums contain 4, so the bigger sum is the one with the bigger second addend. This works for any number: a + 6 > a + 3.
Worked examples
5 + 2 ... 5 + 4 → 2 < 4, so 5 + 2 < 5 + 4.
Out of 10 words Komil made 3 mistakes and Malika 2. Malika got more right: 10 − 2 > 10 − 3.
Class activity
“Quick compare”: the teacher shows two sums and children show “>” or “<” with their arms without calculating.
Practice
1
Without calculating: 3 + 5 ... 3 + 2
>
2
Without calculating: 1 + 6 ... 4 + 6
<
3
Without calculating: 7 + 2 ... 2 + 7
=
4
A dictation has 10 words. The beginning has 7 words. How many more words are needed?
3