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# At some point while traveling to a city Mr. Hock increased his speed

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Re: At some point while traveling to a city Mr. Hock increased his speed [#permalink]
Bunuel wrote:
At some point while traveling to a city Mr. Hock increased his speed by 20%. After traveling for some distance at that speed, he reduced his speed by 15%. After this deduction Mr. Hock's speed was 51 km/hour. What was Mr. Hock's original speed?

A. 42 km/hour
B. 47 km/hour
C. 49 km/hour
D. 50 km/hour
E. 52 km/hour

Let the original speed of Mr. Hock be S miles per hour.

First his speed is increased by 20% and then after travelling some distance at that speed, the speed is

reduced by 15%.

The speed is successively changed by 20% and 15% respectively.

And, the final speed after reduction is 51 miles per hour.

So, the overall percentage change in the speed =[20+(−15)+(20)(−15)100]
% = 2%

The final speed after the increase = S + 2% of S = (1.02) S

(1.02)S=51

S = 50 miles per hour.