Answer:
The average speed will be: 48 km/h
Step-by-step explanation:
FOR FIRST 20 KM
Distance covered by a car = 20 km
Speed at which the first 20 km distance was covered = 40 km/hr
- As we know time equals distance divided by speed.
So
Time taken to cover first 20 km distance= 20 ÷ 40 = 1 ÷ 2 hrs
FOR NEXT 20 KM
Distance = 20 km
Speed at which the next 20 km distance was covered = 60 km/hr
Time taken to cover first 20 km distance = 20 ÷ 60 = 1 ÷3 hrs
so
Total time = Time taken to cover first 20 km distance + Time taken to cover first 20 km distance
[tex]=\frac{1}{2}+\frac{1}{3}[/tex]
[tex]=\frac{3}{6}+\frac{2}{6}[/tex] ∵ [tex]\mathrm{Least\:Common\:Multiplier\:of\:}2,\:3:\:\:6[/tex]
[tex]\mathrm{Since\:the\:denominators\:are\:equal,\:combine\:the\:fractions}:\quad \frac{a}{c}\pm \frac{b}{c}=\frac{a\pm \:b}{c}[/tex]
[tex]=\frac{3+2}{6}[/tex]
[tex]=\frac{5}{6}[/tex]
So total time = 5/6 hours
Thus,
average speed = [tex]\left(20\:+\:20\right)\:\div \left(5\:\div \:6\right)[/tex]
[tex]=\frac{40}{\frac{5}{6}}[/tex]
[tex]=\frac{40\cdot \:6}{5}[/tex] ∵ [tex]\mathrm{Apply\:the\:fraction\:rule}:\:\frac{a}{\frac{b}{c}}=\frac{a\cdot \:\:c}{b}[/tex]
[tex]=\frac{240}{5}[/tex]
[tex]=48[/tex] km/h
Therefore, the average speed will be: 48 km/h
