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Aptitude - Square Root and Cube Root - Discussion

Discussion Forum : Square Root and Cube Root - General Questions (Q.No. 3)
Square Root and Cube Root
3.
The least perfect square, which is divisible by each of 21, 36 and 66 is:
213444
214344
214434
231444
Answer: Option
Explanation:

L.C.M. of 21, 36, 66 = 2772.

Now, 2772 = 2 x 2 x 3 x 3 x 7 x 11

To make it a perfect square, it must be multiplied by 7 x 11.

So, required number = 22 x 32 x 72 x 112 = 213444

Discussion:
80 comments Page 8 of 8.
Laxmi said:   7 years ago
Why should we multiply by 7 and 11? Please tell me.
(1)
Rashmi said:   6 years ago
Please explain the second step.
Maniram said:   6 years ago
Since 213444 is divisible by all of the three number i.e. 21, 36, 66 so its the answer. We don't even have to see the second option.
(6)
Ramesh said:   6 years ago
How to square 7 & 11? Can anyone explain in shortcut method?
(4)
Aayush said:   5 years ago
L.C.M. of 21, 36, 66 = 2772.
Now, 2772 = 2 x 2 x 3 x 3 x 7 x 11.
To make it a perfect square, it must be multiplied by 7 x 11.
So, required number = 22 x 32 x 72 x 112 = 213444.
(4)
Akki said:   5 years ago
Let's solve it by option elimination.

21 divisibility test number should be divisible by 7 and 3,
36 divisibility test number should be divisible by 9 and 4,
66 divisibility test number should be divisible by 11 and 6,
So option A and C are divisible by 11 and B and d are not so discard B and D.
So option C is not a perfect square so the correct answer is Option A.
(14)
Kushi said:   3 years ago
How? Please explain me.
(6)
Shristi said:   3 years ago
Why we have multiplied 2 3 7 11 square? Please explain me.
(6)
Nihal said:   10 months ago
Why should we square 7 and 11? Please explain to me.
(3)
Ram said:   2 weeks ago
Understandable explanations. Thanks all.
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