Aptitude - Square Root and Cube Root - Discussion

Take LCM for 21, 36 and 66 we get 2*2*3*3*7*11 = 2772,

2 and 3 are came 2 times we will get perfect square so multiply this term with 7*11 so we get 2*2*3*3*7*7*11*11 = 213444.

How did u get 7^2 and 11^2?
Should have calculated as 2^2 x 3^2 x 7 x 11 right..?

Guys why we multiply 7 and 11 last step ?

Why should we do 7*7 and 11*11 at last step?

Why we should multiply 11*7?

Give any short cut method for lcm.

How come the 2772? Please give me explanation.

Hi @Swasthik.

According to your method 214434 is also a right answer.

Because 214434 now add alternative nos ie 2+4+3 = 9.

1+4+4 = 9 and when we deduct its 0 so it is also a right answer.

The question is " least perfect square which is divisible by each of 21, 36 and 66 ".

So take the LCM of the numbers.

And in the LCM we get 2772.

Which can be written as factors as "2 x 2 x 3 x 3 x 7 x 11".

In which 2 and 3 are double in number but 7 and 11 are singles.

For finding the least perfect square we have to multiply the number by 7 and 11 so that we have all the factors double in number i.e.

"2x2x3x3x7x7x11x11".

Whose multiplied number will be"213444".

Which will be a perfect square.

Hi friends,

Here I will tell you the simple method to solve.

Just add alternative digit from the given answer eg: 213444.

Now add 2+3+4 = 9.

1+4+4 = 9.

Then deduct 9-9=0 if you get answer is 0. That means it is divisible by given number. :).

21 36 66 are divisible by 3.

Now check the options. And then find the least no. Which is also divisible by 3.