if Henry drove 220 kilometers between 10:00A.M and 1:40 P. M what was his average speed,in kilometers per hour (a) 54 (b) 60 (c) 55(d)45?

Answer 1

1:40 P. M = 13 h 40 min

Time of driving = 13 h 40 min - 10 h = 3 h 40 min

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Remark:

1 h = 60 min

40 min = 40 h / 60 = 20 ∙ 2 h / 20 ∙ 3 = 2 h / 3
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Time of driving = 13 h 40 min - 10 h = 3 h 40 min

3 h + 40 min = 3 h + 2 h / 3 = 9 h / 3 + 2 h / 3 = ( 11 / 3 ) h

Speed = Distance / time.

Speed = 220 / ( 11 / 3 ) = 220 ∙ 3 / 11 = 660 / 11 = 60 km / h

Answer 2

T = 13:40 - 10:00 = 3h-40 min. = 3 2/3 h = 11/3 h.

r = d/T = 220/(11/3) = 220 * 3/11 = 60 km/h.