Compare units of measurement in average speed

 Compare units of measurement in average speed

Example 1:
A bus is traveling at an average speed of 40 miles per hour. What is the equivalent speed in kilometers per hour, rounded to the nearest whole number? (1 mile = 1.60934 kilometers)
Average speed of 40 miles per hour means that at an average the bus is traveling 40 miles in 60 minutes. 
It is given that 1 mile is 1.60934 kilometers. Hence, 40 miles will be  
40 miles × 1.60834 =  64.333 kilometers
The equivalent speed rounded to the nearest whole number is
40 miles per hour  =  64 kilometers per hour

Explanation on conversion: 
For the given speed, the two units of measurement are miles and hour.
For the equivalent speed, the two units of measurement are kilometers and hour.
Since both the speeds are given as per hour, converting miles to kilometers will give the equivalent speed of miles per hour in kilometers per hour.

Example 2:
A bus is traveling at an average speed of 40 miles per hour. What is the equivalent speed in kilometers per minute, rounded to the nearest tenth? (1 mile = 1.60934 kilometers)
For the given speed, the two units of measurement are miles and hour.
For the equivalent speed, the two units of measurement are kilometers and minute.
Unlike Example 1, both the units are different in the given and the equivalent speed. 
The solution consists of two steps.
Step 1 - Convert miles per hour to kilometers per hour 
As in Example 1, 
40 miles per hour  =  40 × 1.60934 kilometers per hour
Step 2 - Convert kilometers per hour to kilometers per minute.
Since 1 hour  =  60 minutes, divide the result from step 1 by 60. This will convert per hour to per minute.
$$\boldsymbol{{\frac {40\times 1.60934}{60}} =  1.0728}$$
The equivalent speed rounded to the nearest tenth is
40 miles per hour  =  1.1 kilometers per minute
Note that if the question asked for equivalent speed in kilometers per second, then the result of step 1 would be divided by 3,600 as 1 hour = 3,600 seconds.

Try the following:
1.  Tara is driving at an average speed of 50 miles per hour. What is the equivalent speed in kilometers per hour, rounded to the nearest whole number? (1 mile = 1.60934 kilometers)
2.  A plane is flying at an average speed of 350 miles per hour. What is the equivalent speed of the plane in kilometers per minute, rounded to the nearest tenth? (1 mile = 1.60934 kilometers)
3.  A bus is traveling at an average speed of 36 kilometers per hour. What is the equivalent speed in feet per second? (1 kilometer = 3,280 feet)

Show/Hide Answers
1.  Both the speeds are given as per hour. Only miles have to be converted to kilometers. 50 × 1.60934 = 80.467 kilometers. Equivalent speed is 80 kilometers per hour.
2.  Convert miles per hour to kilometers per hour. Then, divide by 60 to convert kilometers per hour to kilometers per minute. $${\frac {350\times 1.60934}{60}} =  9.387 = 9.4\ kilometers\ per\ minute$$ 
3.  Convert kilometers per hour to feet per hour. Then, divide by 3,600 to convert kilometers per hour to feet per second (1 hour is 3,600 seconds). $${\frac {36\times 3,280}{3,600}} =  32.8\ feet\ per\ second$$