Step-by-step explanation:
the distance is 2500 m = 2.5 km, which we have to change into miles by using the factor of 1.6.
so, 2.5 km / 1.6 = 1.5625 miles.
or in fractions
5/2 / 16/10 = 5/2 / 8/5 = 5/2 × 5/8 = 25/16 = 1 9/16 miles
Adam drove these 1.5625 miles in 102 seconds.
to get mph we need to transform 102 into 3600 (seconds in an hour).
102x = 3600
x = 3600/102 = 1800/51 = 600/17 = 35.29411765...
(25/16 / 102) × (600/17 / 600/17) =
(25×600 / 16×17) / (102×600 / 17) =
(25×75 / 2×17) / (6 × 600) = (1875 / 34) / 3600 =
55.14705882.../1 hour = 55.14705882... mph
a) Adam was driving 55 mph.
b) now we have to calculate backwards.
he would drive 50 miles in 3600 seconds, so, how many seconds for 25/16 miles ?
the factor is
50 / 25/16 = 50/1 × 16/25 = 50×16 / 25×1 = 2×16 = 32
he drove only 1/32 of the 50 miles.
so, now we need to divide 3600 by 32
3600 / 32 = 225/2 = 112.5 seconds
rounded it should have taken him at least 113 seconds.
