Asked by Anonymous

Jan, Febby, and March are participating a 1kilometer dash-run. Jan completes a lap in 60 minutes, Febby completes a lap in 120 minutes and March completes a lap in 80 minutes. If they all started at the same time, then how long will they meet again?

A. 2 hours
B. 3 hours
C. 3.5 hours
D. 4 hours
Answered by Anonymous
My answer is D please check this
Answered by Bosnian
Answer D is correct.

You can check that.

60 min = 1 h

120 min = 2 h

80 min = 80 min / 60 = 20 ∙ 4 / 20 ∙ 3 = 4 / 3 h

1 km = 1 lap

Jan´s speed = 1 km / h = 1 lap / h

Febby´s speed = 1 km / 2 h = 0.5 lap / h

March´s speed = 1 km / ( 4 / 3 ) h = 3 / 4 km / h = 0.75 lap / h


After 1 h

Jan complete 1 lap , Febby complete 0.5 lap , March complete 0.75 lap

After 2 h

Jan complete 2 laps , Febby complete 2 ∙ 0.5 = 1 lap , March complete 2 ∙ 0.75 = 1.5 laps

After 3 h

Jan complete 3 laps , Febby complete 3 ∙ 0.5 = 1.5 laps , March complete 3 ∙ 0.75 = 2.25 laps

After 3.5 h

Jan complete 3.5 laps , Febby complete 3.5 ∙ 0.5 = 1.75 laps , March complete 3.5 ∙ 0.75 = 2.625 laps

After 4 h

Jan complete 4 laps , Febby complete 4 ∙ 0.5 = 2 laps , March complete 4 ∙ 0.75 = 3 laps

They will meet again when each of them runs the whole number of laps, in this case after 4 hours.
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