1. Find the multiples of 7 which is greater than 56 but less than 77.
2. List all the common factors of the following: (i) 12,18,21 (ii) 20,40,35 (iii) 16,18,7
3. Write all prime numbers between 70 and 90.
4. Write the following numbers as a product of their prime factors:
(i) 70
(ii) 105
(iii) 91
Answers
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Step-by-step explanation:
1. Multiples of 7 = 56 < (63, 70) < 77
2. (i) Factors of 12 = 1, 2, 3, 4, 6, 12
Factors of 18 = 1, 2, 3, 6, 9, 18
Factors of 21 = 1, 3, 7, 21
Common factors = (1 , 3)
(ii) Factors of 20 = 1, 2, 5, 10, 20
Factors of 40 = 1, 2, 4, 5, 8, 10, 20, 40
Factora of 35 = 1, 5, 7, 35
Common factors = (1 , 5)
(iii) Factors of 16 = 1, 2, 4, 8, 16
Factors of 18 = 1, 2, 3, 6, 9
Factors of 7 = 1, 7
Common factors = (1 , 7)
3. (71, 73, 79, 83, 89)
4. (i) 70 = (2×5×7)
(ii) 105 = (3×5×7)
(iii) 91 = (7×13)
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