Q.

By which least number should 1323 be multiplied to get a perfect cube?


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a

5

b

6

c

7

d

8 

answer is C.

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Detailed Solution

It is given that 1323 is multiplied by the smallest number to get a perfect cube.
Find the prime factorization of 1323.
  3 1323 3 441 3 147 7 49 7 7 1 Prime factorization of 1323 = 3×3×3 ¯ ×7×7×1.
From the prime factorization of 1323, clearly, factor 3 occurs in a triplet while 7 doesn’t occur in a triplet.
For a product to be a perfect cube all prime factors should exist in a triplet. So, to complete the triplet number, it needs to be multiplied by 7.
Hence, the smallest number to be multiplied by 1323 to make the product a perfect cube is 7.
Thus, option (3) is correct.
 
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