NCERT Solutions for Class 8 Mathematics Chapter 13
Important NCERT Questions
Direct and Inverse Proportions Chapter 8 Exercise 13.2
NCERT Books for Session 2022-2023
CBSE Board
Questions No: 9
A car takes 2 hours to reach a destination by travelling at the speed of 60 km/hr. How long will it take when the car travels at the speed of 80 km/hr?
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Case-1:
Speed = (Distance/time)
∴ Distance = (Speed × Time)
= (60×2) km
= 120 km.
∴ The car travels a distance of 120 km.
Case-2:
Distance = 120 km.
Speed = 80 km/h
Distance= (Speed× Time)
∴ Time = (Distance/Speed)
= (120/80)
=(3/2) [∵ Dividing 120 and 80 by 40.]
= 1 hour (1×60/2) minutes [∵ 1 hour = 60 minutes.]
= 1 hour 30 minutes.
∴ It will take 1 hour 30 minutes to cover the distance.
Let the number of hours be x.
Speed (in km/hr) 60 80
Time (in hours) 2 x
Here, the speed of car and time are in inverse proportion.
∴ 60/80 = x/2 ⇒ xX80 = 60×2 ⇒ x= 60×2/80=3/2 = (1)1/2 hrs
Hence, the car will take hours (1)1/2 hrs to reach its destination.
Class 8 Maths Chapter 11 Exercise 13.2 Solution in Video
for more answers vist to:
https://www.tiwariacademy.com/ncert-solutions/class-8/maths/chapter-13/