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 3.5mi5280ft12in2.54cm1m1 km ------ x -------- x -------- x --------- x -------- x -------- h 1mi1ft1in100cm1000mAnd 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