Oxford University MAT 2017 Solved Papers

Question : 5 of 10

Marks: +1, -0

Let

a

and

b

be positive integers such that

a+b=20

. What is the maximum value that

a^2 b

can take?

Solution:

Rearranging so that

b=20-a

gives

a^2(20-a)

. Differentiating and setting equal to 0 to find the maximum gives

a=\;{40}/{3}

. The closest integer to this is 13 and so

b=7

. The answer is (d).

Go to Question:

Prev Question

Next Question