Question

Amrit buys some pens at a price of 10 per pen. He also buys an equal number of
pencils at a price of 5 per pencil. By selling them, he makes a 20% profit on pens
and 8% profit on pencils. At the end of the day, all pens and pencils are sold
out and his profit amounts to 240. Find the number of pens he had purchased.​

Answer 1

Step-by-step explanation:

Let the number of pens be x.

Therefore, the number of pencils is also x as "He also buys an equal number of  pencils".

Pen:-

C.P. of 1 pen = Rs.10

C.P. of x pen = Rs.10*x = Rs.10x

Profit % = 20%

Therefore, S.P. = 10x + 20% of 10x = 10x + 20/100*10x = 10x +  2x = Rs.12x

Profit = S.P. - C.P. = 12x - 10x = Rs.2x

Pencil:-

Similarly,

C.P. of 1 pencil = Rs.5

C.P. of x pencil = Rs.5*x = Rs.5x

Profit% = 8%

Therefore, S.P. = 5x + 8% of 5x = 5x + 8/100*5x = 5x + 2x/5 = 25x + 2x/5 = Rs.27x/5.

Profit = S.P. - C.P. = 27x/5 - 5x = Rs.2x/5

Total profit = 2x/5 + 2x = 2x + 10x/5 = Rs.12x/5

Also, total profit = Rs.240

Therefore,

12x/5 = 240

=12x = 960

=x = 960/12 = 80

Answer:- The number of pens he purchased is 80.

Hope it helps!