Question

4-> Perpetua has 1,800/= to buy pencils. There are 2 types which prices differ by 40/=. If she boys the cheaper type sho will get 15 more pencils than if she buys the expensive type. What are the prices of the pencils?​

Answer 1

The price of the two pencils is Rs.100 (expensive) and Rs.60 (cheaper).

Let the price of the expensive pencil be = x

And the price of the cheaper one be = y.

According to the question:

The difference between the price of 2 = 40

Therefore,

x- y =40

Total amount = 1800.

The number of Expensive pencils that can be bought = 1800/x.

The number of Expensive pencils that can be bought = 1800/y.

According to the question,

1800/y -1800/x = 15 (the number of extra pencils)

= (1800x -1800y)/xy = 15

= 1800x -1800y =15xy

= 1800 (x-y) =15xy

Substituting x-y as 40

1800 x 40 =15xy

xy = 4800.

We know that x-y =40

Therefore, x = y+ 40

xy = 4800

(y+40) y = 4800

`y^(2)` + 40 y = 4800

Using the quadratic equation formula,

y = 52.111 or y = -92.111

Thus, the cost of the cheaper pencil (y)= Rs. 52.111

The cost of the expensive pencil (x) = 52.111 + 40 = Rs 92.111

Therefore the cost of two pencils is = Rs. 52.111 and Rs 92.111.