Class 8 chapter 2 CBSE linear equation in one variable

Question

RamRam went to a book shop to purchase three books maths science Hindi each if total cost of maths and Science book is rupees 105 and the cost of math book is rupees 15 more than that of science book find the cost of both the books separately and if if cost of Science and Hindi book are in the ratio 3 ratio 1 then find the cost of Hindi book and find the total money given to shopkeeper by Ram

Answer 1

Let "m" be the cost of the math book. Let "s" be the cost of the science book. And let "h" be the cost of the Hindi book.

m + s = 105

m = s + 15

So, plugging in "s + 15" into the top equation in place of "m" we get:

(s + 15) + s = 105

2s + 15 = 105

2s = 90

s = 45

Then, since m = s + 15, m = 45 + 15 or m = 60

s/h = 3/1

45/h = 3/1

Cross multiplying: (45)(1) = (3)(h)

45 = 3h

h = 15

Total purchase = 45 + 60 + 15 = 120 rupees