Question

Dolma Bought some pens for Rs.90 . If she had paid Re.1 less for each pen , she would have bought 3 more pens. how many pens did she buy....???

Answer 1

If She Paid 1 Re. For each so she has 90 Pens and after she bought 3 more pens So she has (90+3=93) Pens.

Answer 2

Answer:

18

Step-by-step explanation:

According to the question,

Let the pens bought by dolma = x

rate of a pen = y

Then,

$xy = 90~~~~~~~~~~~...(1)$

If she had paid Rs. 1 less for each pen

Then,

Pens bought by dolma = x + 3

Rate of a pen = y - 1

Now,

$(x + 3)(y - 1) = 90\\\\xy +3y - x -3 = 90\\\\90 + 3y - x -3 = 90\\\\3y - x = 3\\\\y = \frac{3+x}{3}$

put y = x + 3 in equation 1st.

$xy = 90\\\\x(\frac{3+x}{3} - 90\\\\x^2 + 3x -270\\\\\\\\x^2 +18x -15x -270 \\\\x(x+18)-15(x+18)\\\\(x-15)(x+18)\\\\So,\\x =15$

x+3 = 15+ 3= 18

Hence, Dolma buy 18 pens.