Question

Ajay walked at an average speed of 8 km/h for 45 minutes and then ran at an average speed of 12 km/h
for 40 minutes. What was his average speed for the whole journey?
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Answer 1

Your Answer:

Given:-

• Ajay walked at an average speed of 8 km/h for 45 minutes
• Then ran at an average speed of 12 km/h  for 40 minutes.

To Find:-

• His average speed for the whole journey.

Solution:-

In case 1 where his speed is 8km/h

time = 45 min = 45/60 hours = 3/4 hours

Distance = speed × time

distance = 8 × 2/4 = 4 km

In case 2 where his speed is 12km/h

time = 40 min = 40/ 60 hours = 2/3 hour

Distance = speed × time

distance = 12 × 2/3 = 8 km

Average speed = total distance / total time

Average speed  $\tt =\dfrac{8+4}{\frac{2}{3}+\frac{3}{4}}$

$\tt=\dfrac{12}{\frac{17}{12}}\\\\\tt= \frac{144}{17}\\\\\tt =8.5 appx$

So average speed is 8.5 km/h