HCF of two numbers is 1/5th of a number and 1/7th of the other number. The difference between the numbers is 42. What is the LCM?
The Usual Method
We know that HCF x LCM = product of two numbers
Let HCF = x
One number = 5x and another number = 7x
LCM = 35x
Also, difference between numbers = 7x – 5x = 2x = 42 (given)
x = 21 = HCF.
LCM = 35 x 21 = 735
Estimated Time to arrive at the answer = 45 seconds.
Looking at the information in the problem, it is evident that the LCM is a multiple of 7 and 5. The only option that is a multiple of 7 and 5 amongst the options is option ‘2’.
Estimated Time to arrive at the answer = 5 seconds.