A bus starts running with some initial speed and its speed increases every hour by 9 km/hr. If it takes 11 hours to cover a distance of 572 km, then what was the initial speed (in km/hr) of the bus?
Let initial speed of bus = $$x$$ km/hr = Distance travelled in 1st hour
Speed after 1 hour = $$(x+9)$$ km/hr = Distance travelled in 2nd hour and so on.
Similarly, distance travelled in 11th hour = $$(x+90)$$ km
Total distance (using sum of an arithmetic series) = $$\frac{11}{2}[(x)+(x+90)]=572$$
=> $$x+45=\frac{572}{11}=52$$
=> $$x=52-45=7$$
$$\therefore$$ Initial speed of bus =Â 7 km/hr
=> Ans - (B)
Create a FREE account and get:
