# A car covers one third of the distance with 20 kmph and the rest with 60 kmph.The average spped of the car is

2
by rinky1

2015-07-23T17:15:28+05:30

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Let the total distance to cover = d km

one third of the distance is covered with 20 kmph
So d₁ = d/3
v₁ = 20 km/h
t₁ = d₁/v₁ = (d/3)/20 = d/(3*20) = d/60 hour

Rest distance, d₂ = 2d/3
v₂ = 60 kmph
t₂ = d₂/v₂ = (2d/3) / 60 = d/90 hour

total time,t = t₁ + t₂ = d/60 + d/90 = 5d/180 = d/36 hour

average speed = d/t = d/(d/36) = 36 km/h
• Brainly User
2015-07-28T12:24:32+05:30

### This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
LET TOTAL DISTANCE = X km

X1 = X/3 km
V1 = 20 km/h
X2 = 2X/3 km
V2 = 60 km/h

SPEED = DISTANCE / TIME

TIME = DISTANCE / SPEED

t1 = X1 / V1
t1  = X / 60 h

t2 = X2 / V2
t2 = X / 90 h

TOTAL TIME,

t = t1 + t2

t = X / 60 + X / 90 = X / 36 h

AVERAGE SPEED = DISTANCE / TIME
=  X / (X/36)

=
36 km/h