# Q.1 Find the common factors of: (a) 20 and 28 (b) 15 and 25 (c) 35 and 50 (d) 56 and 120

(a) 20 and 28
Factors of 20 are 1, 2, 4, 5, 10, 20
Factors of 28 $$\rightarrow$$ 1, 2, 4, 7, 28
Hence, the common factors $$\rightarrow$$ 1, 2 and 4.
(b) 15 and 25
Factors of 15 $$\rightarrow$$ 1, 3, 5, 15
Factors of 25 $$\rightarrow$$1, 5, 25
Hence, the common factors are 1 and 5.
(c) 35 and 50
Factors of 35 $$\rightarrow$$ 1, 5, 7, 35
Factors of 50 $$\rightarrow$$ 1, 2, 5, 10, 50
Hence, the common factors are 1 and 5.
(d) 56 and 120
Factors of 56 $$\rightarrow$$ 1, 2, 4, 7, 8, 14, 28, 56
Factors of 120 $$\rightarrow$$ 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 30, 40, 60, 120
Hence, the common factors are 1,2, 4, and 8.