Question

i bought 15 books and 12 pens. Their average cost is 70.50 .If the average cost of the 12 pens is rs4.50,what is the average cost of the books?

Answer 1

✒Answer:

The average cost of 15 books is Rs 28.20

✒Step-by-step explanation:

Let the average cost of books be x.

Total average cost = Rs 70.50

By equation,

$\frac{4.50 + 15x}{12 + 15} = 70.50 \\ = > \frac{4.50 + 15x}{27} = 70.50 \\ = >4.50 + 15x = 1903.50 \\ = > 15x = \frac{1903.50}{4.50} \\ = > 15x = 423 \\ = > x = \frac{423}{15} \\ = > x = 28.20$

Hope it helps you.