Tom can walk 3.5 miles per hour; how long will it
take him to travel 3.6 kilometers?
3.5 mi
------
h
Multiply that by a fraction that equals 1, which has
miles on the bottom to cancel out the miles on the top.
We create such a fraction by using the fact that
5280 ft = 1 mile
3.5 mi 5280 ft
------ x --------
h 1 mi
Multiply that by a fraction that equals 1, which has
feet on the bottom to cancel out the feet on the top.
We create such a fraction by using the fact that
12 in = 1 ft
3.5 mi 5280 ft 12 in
------ x -------- x --------
h 1 mi 1 ft
Multiply that by a fraction that equals 1, which has
inches on the bottom to cancel out the inches on the top.
We create such a fraction by using the fact that
1 in = 2.54 cm
3.5 mi 5280 ft 12 in 2.54 cm
------ x -------- x -------- x ---------
h 1 mi 1 ft 1 in
Multiply that by a fraction that equals 1, which has
cm on the bottom to cancel out the cm on the top.
We create such a fraction by using the fact that
100 cm = 1 m
3.5 mi 5280 ft 12 in 2.54 cm 1 m
------ x -------- x -------- x --------- x --------
h 1 mi 1 ft 1 in 100 cm
Multiply that by a fraction that equals 1, which has
m on the bottom to cancel out the m on the top.
We create such a fraction by using the fact that
1000 m = 1 km
3.5 mi 5280 ft 12 in 2.54 cm 1 m 1 km
------ x -------- x -------- x --------- x -------- x --------
h 1 mi 1 ft 1 in 100 cm 1000 m
Now cancel out all the units
3.5 mi 5280 ft 12 in 2.54 cm 1 m 1 km
------ x -------- x -------- x --------- x -------- x --------
h 1 mi 1 ft 1 in 100 cm 1000 m
And we are left with just
(3.5)(5280)(12)(2.54)(1)(1) km 563270.4 km 5.632704 km
-------------------------------- = ------------- = -------------
h(100)(1000) 100000 h h
So his rate = 5.63704 km/h
Since TIME = DISTANCE/RATE, his time to go 3.6 km =
= 3.6/5.63704 = .6391246549 h or 38.34747929 minutes
or about 38 minutes 21 seconds.
Edwin
