question_answer

Which of the following numbers are co-prime?

(a) 18 and 35

(b) 15 and 37

(c) 30 and 415

(d) 17 and 68

(e) 216 and 215

(f) 81 and 16

Answer:

Number	Factors	Common factor	Co-prime
18 and 35	18 = 1, 2, 3, 6, 9 and 18 35 = 1, 5, 7 and 35	1	Thus 18 and 35 are co-prime.
15 and 37	15 = 1,3,5 and 15    37 = 1 and 37	1	Thus 15 and 37 are co-prime
30 and 415	30 = 1,2, 3,5,6,15,30 415 = 1, 5....	1, 5	Thus 30 and 415 are not co-prime
17 and 68	17 = 1 and 17 68 = 1, 2, 4, 17,	1, 17	Thus 17 and 68 are not co-prime
216 and 215	216=1, 2, 3, 4, 6....... 215 = 1, 5,	1	Thus 216 and 215 are co-prime
81 and 16	81 =1, 3, 9.... 16 = 1, 2, 4, 8, 16	1	Thus 81 and 16 are co-prime