Question

14:16::630:x
From ratio proportion and unitary method​

Answer 1

Answer:

Each book costs Rs 4 and 15 books are purchased.

Step-by-step explanation:

Define x:

Let the number of books be x

Find the cost of 1 book:

Total cost of the books = Rs 60

Cost of 1 book = 60 ÷ x = 60/x

Find the new price if it decrease by Rs 1:

New Price = 60/x - 1

Solve x:

Cost of book decreased by Rs 1, number of purchase increased by 5

(60/x - 1)(x + 5) = 60

60 + 300/x - x - 5 = 60

300/x - x - 5 = 0

300 - x² - 5x = 0

x² + 5x - 300 = 0

(x - 15)(x + 20) = 0

x = 15 or x = -20 (rejected, since books purchased cannot be negative)

Find the number of books purchased:

Number of books = x = 15

Find the cost of a book:

Total cost = Rs 60

Number of books = 15

Cost of a book = 60 ÷ 15 = Rs 4

Answer: Each book costs Rs 4 and 15 books are purchased.