A, B and C start swimming in a pool simultaneously from the

Question

A, B and C start swimming in a pool simultaneously from the same end. To complete 10 laps, A takes 10 minutes, B takes 8 minutes and C takes 6 minutes. What is the ratio of speeds A:B:C?

A. 3:4:5
B. 12:15:20
C. 5:4:3
D. 4:6:5
E. 12:15:25

coolredwine · Answer

This is a very good trap question. I am sure many people would have seen the options and just marked C.

PareshGmat · Answer

B. 12:15:20

Speed Of A = \frac{10}{10}

Speed of B  = \frac{10}{8}

Speed of C  = \frac{10}{6}

Ratio  = \frac{1}{10} : \frac{1}{8} : \frac{1}{6}

= \frac{1}{5} : \frac{1}{4} : \frac{1}{3}

= 12 : 15 : 20 = Answer = B

Bunuel · Answer

The slowest one is A, then comes B and the fastest one is C. So, the the ratio of speeds A:B:C must be in ascending order. Eliminate options C, D, and E.

A's speed (distance)/(time) = 10/10 = 1 lap per minute = 12 laps in 12 minute; 
B's speed (distance)/(time) = 10/8 = 5/4 lap per minute = 15 laps in 12 minutes; 
C's speed (distance)/(time) = 10/6 = 5/3 lap per minute = 20 laps in 12 minutes/

Therefore, the the ratio of speeds A:B:C is 12:15:20.

Answer: B.

Hope it's clear.

GyanOne · Answer

As distance (= speed x time) is constant for all three, the ratios of their speeds will be the reciprocals of the times taken by them.

=> Ratio of speeds (A:B:C) = 1/10 : 1/8 : 1/6 = 12:15:20 (multiplying throughout by 120)

Option (B).

sanjoo · Answer

10/10:5/4:5/3 1:5/4:5/3 multiply 4 (denominator of 5/4) to both other ratios.. 4:5:20/3===and now multiply 3(denomonitor of 20/3) other two ratios.. 12:15:20..:D

option B...

OptimusPrepJanielle · Answer

A, B and C start swimming in a pool simultaneously from the same end. To complete 10 laps, A takes 10 minutes, B takes 8 minutes and C takes 6 minutes. What is the ratio of speeds A:B:C?

To make the rates comparable we can make the denominator 120 minutes. We should multiply the numerator and denominator by 12, 15, and 20, respectively.

10 laps/ 10 minutes = 120 laps/120 minutes
10 laps/8 minutes = 150 laps/120 minutes
10 laps/6 minutes = 200 laps/120 minutes

120:150:200 can be simplified by dividing each by 10.

A. 3:4:5
 B.  12:15:20
C. 5:4:3
D. 4:6:5
E. 12:15:25

kapstone1996 · Answer

Distance = Rate * Time,

Each doing 10 laps so distance is the same.

I used the LCM of 10,8,6 = 120 for distance

So 
A = Distance (120) / Time (10) = Rate of 12
B = Distance (120) / Time (8) = Rate of 15
C = Distance (120) / Time (6) = Rate of 20

so ratio of 12, 15, 20

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