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 ?

20 mangoes.

Step-by-step explanation:

Given:

Total  number of mangoes, a trader bought =

A trader bought at the rate of 4 mangoes for 10 naira.

Five of the mangoes were bad.

He sold the remaining at the rate of 5 mangoes for 20 naira.

He made a gain of 10 naira

Question asked:

Total  number of mangoes, a trader bought = = ?

Solution:

Unitary method

Cost price of  4 mangoes =  10 naira.

Cost price of  1 mango =

Cost price of mango =

As 5 of the mangoes were bad and he sold the remaining mangoes, then Total number of mangoes sold =  

Sale price of 5 mangoes = 20 naira

Sale price of 1 mango =

Sale price of mango =

Now, as we know,

Adding both sides by 20

Multiplying both sides by 2

Dividing both sides by 3

Therefore, total number of mangoes, a trader bought is 20.