Numbers -1

Find the minimum perfect square divisible by 3,4,5, and 7 ?
(A) 44100        (B) 8820      (C) 14700         (D) 8820 (E) None of these

Solution:

Given numbers are: 3,4,5, and 7

To find minimum perfect square divisible by a group of numbers, first make each number of the group a perfect square and then find LCM.

3 is not a perfect square, hence consider 3² = 9

4 is a perfect square, hence nothing can be done on it

5 is not a perfect square, hence consider 5² = 25

7 is not a perfect square, hence consider 7² = 49

Now, we need a number which is divisible by these numbers. For that we need to find LCM of 9,4,25,49. As these numbers are co-prime, LCM is nothing but simple multiplication:

9 * 4 * 25 * 49 = 44100     

Answer (A)