3. Class 8 Mathematics 3rd Model Test Paper

1. If you subtract 12 from a number and multiply the result by 12 , you get 18 . What is the number?

Solution : let, x be the number .

A/Q ,

x-12×12=18

⇒2x-12×12=18

⇒2x-14=18

⇒2x-1=18×4

⇒2x-1=12

⇒2x=12+1

⇒2x=1+22

⇒2x=32

⇒x=32×2

⇒x=34
Therefore, the number is 34 .

2. The perimeter of a rectangular swimming pool is 154 m. Its length is 2 m more than twice its breadth. What are the length and the breadth of the pool?

Solution : let x (in metres) be the breadth of the rectangular swimming pool and the length of the rectangular swimming pool will be 2x+2 .

Here , breadth (b)=x and length  (l)=2x+2

A/Q , 2l+b=154

⇒22x+2+x=154

⇒23x+2=154

⇒6x+4=154

⇒6x=154-4

⇒6x=150

⇒x=1506

⇒x=25

Therefore, the breadth is 25 m and the length is 2×25+2=50+2=52 m .