Question

The smallest number that is a perfect square and which can be divided by 7, 12,14 and 21 is

Answer 1

First let us factories the given numbers and see their powers.
8 = 2^3
12 = 2^2 x 3
15 = 3 x 5
20 = 2^2 x 5

So a number which is divisible by each of them should contain 

2^3 x 3 x 5

Now for it to be a perfect square, it should have even powers

Hence, 

2^4 x 3^2 x 5^2 is sufficient and least number which will satisfy all conditions.
3600 is the answer

Please mark it as brainiest answer ............

Answer 2

let us take a number which is divisible by 21
n should be perfect square=21²=441 is divisible by 21
but not by 14 = 441÷14 = 31.5
so the number which is divisible by both is 882 but it is not by 12
= 882÷12
= 73.5
so a number which is divisible by thrice is 1764 
and it is also divisible by 7 and 21,14,12
and it is square of 42