Mon February 11, 2013 By:

How far in kilometers can Sumit drive into the company if he drives out at 40 kilometers per hour (kmph), returns over the same road at 30 kmph, and spends 8 hours away from home, including a one hour stop for lunch? Please explain how.

Expert Reply
Wed February 13, 2013

Sumit's actual driving time is 7 hours, which must be divided into two parts: his time spent driving into the company and his time spent returning.

Let the first part equals x, then the return  time will be 7 - x.

We know:

Rate x time = distance

Going: (40)(x) = 40x

Returning: (30)(7 - x) = 210 - 30x

Because the journey is round trip, the distance going equal the distance returning.

Thus, we have:

40x = 210 - 30x

70x = 210

x = 3

Hence, Sumit travelled 40 km/r fot 3 hours, so he travelled 120 km.
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