Which of the following pairs of numbers is not coprime?
(171, 273)
Two numbers are coprime when their highest common factor (HCF) is 1; they are not coprime if they share a common factor greater than 1.
For (127, 257): 127 and 257 are both prime, so their HCF is 1 and they are coprime.
For (173, 351): 173 is prime and does not divide 351, so their HCF is 1 and they are coprime.
For (177, 827): 177 = 3 × 59 and 827 is prime, sharing no common factor, so HCF is 1 and they are coprime.
For (171, 273): 171 = 3 × 57 and 273 = 3 × 91, so both are divisible by 3, giving HCF 3.
Hence, the pair that is not coprime is (171, 273).
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Important Questions from LCM and HCF
The HCF and LCM of two numbers are 12 and 72, respectively. If the ratio of the two numbers is 2 ∶ 3, then the larger of the two numbers is:
Find the greatest number that will divide 43, 91 and 183 so as to leave the same remainder in each case.
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The sum of two numbers is 1215 and their HCF is 81. How many such pairs of numbers can be formed?
The LCM of two numbers in 48. Their ratio is 2:3 What is the sum of the numbers?
