Find the LCM of , and .
The Usual Method
First find the LCM of the numerators = 4 x 3 x 5 = 60
HCF of denominators = 1
LCM of fractions = LCM of numerators
HCF of denominators
= = 60
Estimated Time to arrive at the answer = 30 seconds.
Since HCF of any set with a prime number in it is always 1, denominator will be = 1. This eliminates options ‘1’ and ‘5’.
LCM of numerators = product of numerators if they are relatively prime
Hence LCM of the numerators = 4 x 3 x 5 = 60
Hence answer = 60
(Note: The example here is seemingly simple but the important part is the approach in the technique. This approach is universal in its application and so can be applied to other more complex problems also).
Estimated Time to arrive at the answer = 10 seconds.