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Number System · Question 61 of 71

Question 61

MediumOriginal question

By what smallest number should 1,350 be divided so that the quotient is a perfect cube?

Options for question 61

Show the answer and explanation
CorrectNot quiteAnswer D

Correct answer: D

Explanation

  1. 1,350=2×33×521{,}350 = 2 \times 3^3 \times 5^2.

  2. For a cube every power must be a multiple of 3; 333^3 is fine, but 2 and 525^2 are not.

  3. Divide by 2×52=502 \times 5^2 = 50: 1,350÷50=27=331{,}350 \div 50 = 27 = 3^3.

Worth noting

Dividing by just 2 leaves 675=33×52675 = 3^3 \times 5^2, still not a cube; both leftover primes must go.

Concept
Smallest divisor to obtain a perfect cube
Typical time
60 s
Your time
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The rule this testsFactors and prime numbers
Practise this chapter →

Ten questions from Number System, at your own pace.

Practise this chapter →

Ten questions from Number System, at your own pace.