The Product is 2016, But Minimize the Sum

The product of three natural numbers is equal to 2016. What's the least possible value for their sum?

39 41 43 38 40

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3 solutions

Sherwin D'souza
Jan 16, 2016

You can even use AM GM inequality.

a + b + c 3 a b c 3 \frac{a+b+c}{3}≥\sqrt[3]{abc}

Given that abc=2016,

a + b + c 3 × 2016 3 a+b+c≥3 \times \sqrt[3]{2016} => a + b + c 3 × 12.633 a+b+c≥3 \times 12.633

For minimum value, a + b + c = 3 × 12.633 = > a + b + c = 37.899 38 a+b+c=3 \times 12.633 =>a+b+c=37.899 ≈\boxed{38}

This proves that no sum less than 38 38 is possible, but this fact alone does not give the answer. We still need to factorize 2016 2016 and discover that ( 12 , 12 , 14 ) (12, 12, 14) is a solution to conclude that the answer is 38 38 .

Daniel Ploch - 5 years, 4 months ago
Atul Shivam
Jan 15, 2016

first of all 2016 = 2 5 × 3 2 × 7 2016=2^5×3^2×7 we must have to choose three numbers whose sum is minimum so these numbers must be close to each other to give minimum value , I got these numbers as 12 , 12 , 14 12,12,14 which upon adding gives 38 \boxed{38} which was already their in options so I got help from options as well :-)

Nagarjuna Reddy
Jan 13, 2016

2016=4×504=4×4×126=4×4×14×9= 4×4×14×3×3=12×12×14. To see the sum minimum the nubers must be as close as possible to each other. So 12+12+14=38.

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