John walking at a speed of 20 km/h reaches his college 10 mins late. Next time he increases his speed by 5 km/h, but finds that he is still late by 4 mins. What is the distance of his college from his house.
(a) 20 km
(b) 6 km
(c) 12 km
(d) none of these
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jrbrown2
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We know that the distance to college remains constant.
D = Distance
T = Time to reach college on time
We know that @ 20 km/h John was 10 minutes late
D = 20km/h(T+10)
We know that @ 25 km/h John was 4 minutes late
D = 25km/h(T+4)
Equating the 2 equations
20(T+10) = 25(T+4)
T = 20 Minutes
Use one of those equations to determine distance
20km/h(20+10 min)(1h/60 min) = 10 km
D = Distance
T = Time to reach college on time
We know that @ 20 km/h John was 10 minutes late
D = 20km/h(T+10)
We know that @ 25 km/h John was 4 minutes late
D = 25km/h(T+4)
Equating the 2 equations
20(T+10) = 25(T+4)
T = 20 Minutes
Use one of those equations to determine distance
20km/h(20+10 min)(1h/60 min) = 10 km
