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20 Apr 2017, 23:49
Kudos
Bookmarks
B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
75%
(hard)
Question Stats:
57% (02:13) correct
43%
(02:19)
wrong
based on 352
sessions
History
Date
Time
Result
Not Attempted Yet
One pump drains one-half of a pond in 3 hours, and then a second pump starts draining the pond. The two pumps working together finish emptying the pond in one-half hour. How long would it take the second pump to drain the pond if it had to do the job alone?
A. 1 hour
B. 1.2 hours
C. 3 hours
D. 5 hours
E. 6 hours
A. 1 hour
B. 1.2 hours
C. 3 hours
D. 5 hours
E. 6 hours
21 Apr 2017, 01:37
Kudos
Bookmarks
Rate at which First Pump drains = P1
Rate at which Second Pump drains = P2
Given
(1/P1) * 3 = W/2 [ W here represents the complete work of draining the pond] -- Equation 1
1/P1 = W/6 --> Substituting this in Equation 1
(1/P1 + 1/P2) * 1/2 = W/2 -- Equation 2
W/6 + 1/P2 = W
1/P2 = 5W/6
1/P2 * 6/5 = W
Therefore the second pump will take 6/5 hr or 1.2 hrs to drain the pond on it's own.
Answer is B. 1.2 hours
Rate at which Second Pump drains = P2
Given
(1/P1) * 3 = W/2 [ W here represents the complete work of draining the pond] -- Equation 1
1/P1 = W/6 --> Substituting this in Equation 1
(1/P1 + 1/P2) * 1/2 = W/2 -- Equation 2
W/6 + 1/P2 = W
1/P2 = 5W/6
1/P2 * 6/5 = W
Therefore the second pump will take 6/5 hr or 1.2 hrs to drain the pond on it's own.
Answer is B. 1.2 hours
21 Apr 2017, 03:22
Kudos
Bookmarks
given pump drains one half in 3 hrs,,so full in 6 hrs... also half of the work is done. so half left
rate of one pump is 1/6..
let x be the time taken by the second pump to empty the pond
rate of second pump is 1/x ..
to complete second half of the work,
rate * time = work
(1/6 + 1/x) * 1/2 = 1/2
solve for x = 6/5 = 1.2 hrs,,
ans B
rate of one pump is 1/6..
let x be the time taken by the second pump to empty the pond
rate of second pump is 1/x ..
to complete second half of the work,
rate * time = work
(1/6 + 1/x) * 1/2 = 1/2
solve for x = 6/5 = 1.2 hrs,,
ans B
