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19 Oct 2021, 07:30
Kudos
Bookmarks
A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
15%
(low)
Question Stats:
81% (01:24) correct
19%
(01:40)
wrong
based on 123
sessions
History
Date
Time
Result
Not Attempted Yet
Gary can polish a floor in 4 hours. If Brian can work twice as fast as Gary and Dianne can work twice as fast as Brian, how many hours would it take all three of them, working together but independently, to polish the floor?
(A) 4/7
(B) 5/6
(C) 1
(D) 3/2
(E) 7/4
(A) 4/7
(B) 5/6
(C) 1
(D) 3/2
(E) 7/4
19 Oct 2021, 10:43
Kudos
Bookmarks
Rate at Grey work = 1/4 units
Rate at Brain work = 2*(1/4) = 1/2 units
Rate at Dianne work = 2*(1/2) = 1 unit
Rate at all 3 work together = (1/4) + (1/2) + 1 = (7/4)
Work done = 1 / Rate = 1 / (7/4) = 4/7 = Option A
Posted from my mobile device
Rate at Brain work = 2*(1/4) = 1/2 units
Rate at Dianne work = 2*(1/2) = 1 unit
Rate at all 3 work together = (1/4) + (1/2) + 1 = (7/4)
Work done = 1 / Rate = 1 / (7/4) = 4/7 = Option A
Posted from my mobile device
19 Oct 2021, 10:54
Kudos
Bookmarks
Bunuel
Let total work be 4 units...
Efficiency of Gary be 1 unit/Hr ; Efficiency of Brian will be 2 unit/Hr & Efficiency of Dianne will be 4 unit/Hr
Combined efficiency of Gary , Brian & Dianne will be 1 + 2 + 4 = 7 units/Hr
Thus, Time required if all three of them, working together but independently, to polish the floor is 4/7, Answer will be (A)
