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20 Mar 2026, 22:44
Kudos
Bookmarks
C
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:
54% (02:55) correct
46%
(03:18)
wrong
based on 26
sessions
History
Date
Time
Result
Not Attempted Yet
Forgeform has a new machine and an older machine that each requires the same warm-up time before working at constant rates. Including the warm-up time, the new machine completes a task in 16 minutes, whereas the older machine completes the task in 28 minutes. Working together, the two machines complete the task in 12 minutes, including the warm-up time. How long is the warm-up time?
A. 2 minutes
B. 3 minutes
C. 4 minutes
D. 5 minutes
E. 6 minutes
A. 2 minutes
B. 3 minutes
C. 4 minutes
D. 5 minutes
E. 6 minutes
24 Mar 2026, 00:33
Kudos
Bookmarks
kevincan
Older machine = warm up time + work time = t + work time = 28
Newer machine = warm up time + Work time = t + work time = 16
Combined = t + work time = 12
1/(16-t) + 1/(28-t) = 1/(12-t)
Logically substituting values will yield answer. To start with ignore the odd values, as the subtraction from an even number should provide an even number.
Using t=2 , we get 14 and 26. Doesn’t suit.
Shifting to t=4 matches both sides.
(1/12) + (1/24) = (1/8)
Option C (4 minutes)
