Question

Lily takes 3 hours to travel from place A to place B at the speed of 60 miles per hour. She takes 2 hours to travel from place B to C with a speed increased by 50 %. Find the average speed from place A to C.

• A. 108 miles/hr
• B. 78 miles/hr
• C. 72 miles/hr
• D. 115 miles/hr

Answer 1

The correct option is C

72 miles/hr

Given,
Speed ( from A to B ) $=60\text{mile/hour}$
Speed ( from B to C ) $=60+0.5\left(60\right)=60+30=90\text{mile/hr}$
(Speed is increased by 50% ).

$\text{Distance}=\text{Speed}\times \text{Time}$

Distance from A to B = $60\times 3=180\text{miles}$.

Distance from B to C$=90\times 2=180\text{miles}$

Total ditance travelled $=180+180=360\text{miles}$

Total time taken $=3+2=5\text{hr}$

$\therefore \text{Average speed}=\frac{\text{Total distance}}{\text{Total time}}$

$=\frac{360}{5}=72\text{miles/hr}$