Question

A trader bought x mangoes at the rate of 4 mangoes for 10 naira, five of the mangoes were bad so he sold the remaining at the rate of 5 mangoes for 20 naira and he made a gain of 10 naira how many mangoes did he buy?

Answer 1

Answer:

  20

Step-by-step explanation:

The cost of the x mangoes was ...

  c = 10(x/4)

The revenue from the sale of mangoes was ...

  r = 20(x-5)/5

The profit is the difference between revenue and cost:

  10 = r - c = 20(x -5)/5 -10(x/4) = 1.5x -20 . . . . substitute and simplify

  30 = 1.5x . . . . . add 20

  20 = x . . . . . . . .divide by 1.5

The trader bought 20 mangoes.

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Check

He paid 20(10/4) = 50 naira. He sold the 15 good mangoes for 20/5(15) = 60 naira, so made a 10 naira profit.