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KIRAN NATH S

· started a discussion

· 1 Months ago

doubt (Question: 97568.0 )

When the speed is increased by 50%, how come time is reduced by 33.33% ?

Question:
The speed of a car during the second hour of its journey is thrice that in the first hour. Also its third hours speed is the average speed of the first two hours. Had the car travelled at the second hour’s speed during all the first three hours, then it would have travelled 150 km more. Find the percentage reduction in time if the original distance covered by second hour’s speed:
Options:
A) \(33\frac{1}{3}\%\)
B) 40%
C) 25%
D) 50%
Solution:

Ans: (a)               

                       First               Second       Third      Total

                       hour                 hour         hour

Initial speed       x                     3x          2x             6x

New speed         3x                   3x          3x             9x

∴ Percentage increase in speed = \(\cfrac{3x}{6x}\) × 100 = 50%

Since speed is increased by (50%)  \(\cfrac{1}{2}\)

Therefore, time will reduce by (33.33%) \(\cfrac{1}{3}\)

Knowledge Expert

· commented

· 1 Months ago

Dear student
Given answer is correct
In last line is clear to Decraese the time is 1/3

Best wishes
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