Average Speed-RRB

Average Speed

Computation of average speed is a trickier type of average problems. Average speed uses the formula:

Example 1:

John drove for 3 hours at a rate of 50 miles per hour and for 2 hours at 60 miles per hour. What was his average speed for the whole journey?

Solution:

Step 1: The formula for distance is

Distance = Rate × Time 
Total distance = 50 × 3 + 60 × 2 = 270

Step 2: Total time = 3 + 2 = 5

Step 3: Using the formula

Answer: The average speed is 54 miles per hour.

Example 2:

In travelling from Pune to Nagpur , Rahul drove his bike for 2 hours at 60 kmph and 3 hours at 70 kmph.

Solution: We know that, Distance = Speed × Time

So, in 2 hours, distance covered = 2 × 60 = 120 km in the next 3 hours, distance covered = 3 × 70 = 210 km

Total distance covered = 120 + 210 = 330 km

Total time = 2 + 3 = 5 hrs

Avg. Speed = $\frac{Totaldistancecovered}{}$

$\frac{Timetake\mathrm{n\; =}}{}$Avg. Speed = 330/5 = 66 kmph