122
Divisors and multiples
Textbook: Part 3, lesson 115, pp. 92–93
GoalThe ideas of divisor and multiple; find divisors and multiples of a number.
New words
divisor · bo‘luvchimultiple · karraliis divisible · bo‘linadifactor · ko‘paytuvchi
Explanation
If a is divisible by b with nothing left over, then a is a multiple of b and b is a divisor of a. 45 = 9 × 5, so 45 is a multiple of both 9 and 5, and 9 and 5 are divisors of 45. The divisors of 12 are 1, 2, 3, 4, 6, 12; 5 is not a divisor because 12 is not divisible by 5.
Worked examples
28 = 7 × 4: 28 is a multiple of 7 and of 4.
The divisors of 30 from 2 to 9 are 2, 3, 5, 6.
Class activity
“Hunting multiples”: on a 1–50 number chart children colour the multiples of 7 in one colour and of 9 in another.
Practice
1
From 21, 30, 35, 40, 42, 56, 64 write the multiples of 7.
21, 35, 42, 56
2
From 18, 19, 27, 40, 54, 63, 70 write the multiples of 9.
18, 27, 54, 63
3
Among 2, 3, 4, 5, 6, 7, 8, 9 write the divisors of 30.
2, 3, 5, 6
4
A two-digit number is a multiple of 7 and its first digit is 5. Which number is it?
56
5
1 kg of rice needs 2 l of water. How many litres of water do 7 kg of rice need?
14