TyrionLannister wrote:
Bricklayer Brenda would take 9 hours to build a chimney alone, and bricklayer Brandon would take 10 hours to build it alone. When they work together, they talk a lot, and their combined output is decreased by 10 bricks per hour. Working together, they build the chimney in 5 hours. How many bricks are in the chimney?
(A) 500 (B) 900 (C) 950 (D) 1000 (E) 1900
Brenda is doing 11.11% of the work in one hour.
Brandon does 10% of the work in 1 hour.
So, working together they should do 21.11% of the work in 1 hour.
However, together they take 5 hours,i.e. 20% of work per hour.
i.e. output has decreased by 1.11% per hour
1.11%=10 bricks
==>100%=1000/1.11=900 bricks
Ans:B
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