Math, asked by hargunk3329, 9 months ago

Dinesh what some books for rupees 1200 Gori bought 4 more books for the same amount of money . th average cost of each books is rs. 10 less than the average cost of Dinesh bought .how many books did dinesh buy.​

Answers

Answered by rahulsaab8808
2

Answer:

let the shopkeeper bought x number of books for Rs.1200

price for each book = 1200/x

If he had bought 10 more books for the same amount each book would have cost Rs 20 less

it means

the cost of each books is decreased by 20 if he had bought 10 more books

I.e.

ATQ

1200/x - 1200/x + 10 = 20

1200(1/x - 1/(x+10) = 20

1/x - 1/x+10 = 20/1200

(x+10) - x /x(x+10) = 1/60

x+10 -x = x² + 10x / 60

600 = x² + 10x

x² + 10x - 600 = 0

Here quadratic equation formed ...

x² + 10x - 600 = 0

x² + 30x - 20x - 600 = 0

x(x+30) -20(x+30) = 0

(x+30) (x-20) = 0

either

(x+30) =0 or (x-20) = 0

x = -30 or x = 20

x = -30 X not possible because the number of books cant be negative

so number of books = x = 20

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