Question

A car travels at a speed of 50 $\frac{km}{hr}$ for 30 min, 40 $\frac{km}{hr}$ for the next 15 min, and 60 km/h for the next 60 min. Calculate the average speed of the car

• A. 26.12 $\frac{km}{hr}$
• B. 34.59 $\frac{km}{hr}$
• C. 43.95 $\frac{km}{hr}$
• D. 54.29 $\frac{km}{hr}$

Answer 1

The correct option is D

54.29 $\frac{km}{hr}$

Step 1: Given data

1. Speed S₁= 50 km/hr for time t₁ = 30 minutes = 0.5 hr.
2. Speed S₂ = 40 km/hr for time t₂ = 15 minutes =0.25 hr.
3. Speed S₃ =60 km/hr for time t₃ =60 minutes = 1 hr.

Average speed S = ?

Step 2: Calculation of Average speed

Speed =$\frac{Dis\tan ce}{time}$

so,

Distance = speed $\times$time

1. Distance X₁ = S₁$\times$t₁

= 50 $\times$0.5

= 25 km

2. Distance X₂ = 40 $\times$0.25

= 10 km

3. Distance X₃= 60 $\times$1

=60 km

Total distance = 25 + 10 + 60

X= 95 km

Total time taken T= 0.5 + 0.25 + 1

T = 1.75 hr

Average speed =$\frac{Totaldis\tan ce}{totaltimetaken}$ = $\frac{95}{1.75}$= 54.29 $\frac{km}{hr}$

Hence, the average speed of the car is $54.29\frac{km}{hr}$.Hence option (d) is correct.