N old brainteaser by the Central Asian scholar Biruni (973-1048) : If 10 dirhams (a unit of currency) earn 5 dirhams of profit in 2 months, how much profit will 8 dirhams earn in 3 months?

Question

Myla

Mathematics

11 April, 21:50

N old brainteaser by the Central Asian scholar Biruni (973-1048) : If 10 dirhams (a unit of currency) earn 5 dirhams of profit in 2 months, how much profit will 8 dirhams earn in 3 months?

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Answers (1)

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Lillianna Massey · Answer 1

This is a tricky question because you might use the ratio and proportion method. However, there are 3 terms involved. To cut it down to 2, let's lump the profit rate. The solution is as follows:

10:5/2::8:x/3

Solving for x,

20/5 = 24/x

x = 24 (5) / 20 = 6

Hence, it will earn 6 dirhams of profit.