Jinglander wrote:
Lindsay can paint 1/x of a certain room in one hour. If Lindsay and Joseph, working together at their respective rates, can paint the room in one hour, what fraction of the room can Joseph paint in 20 minutes?
A. \(\frac{1}{3x}\)
B. \(\frac{x}{(x-3)}\)
C. \(\frac{(x-1)}{3x}\)
D. \(\frac{x}{(x-1)}\)
E. \(\frac{(x-1)}{x}\)
If the algebraic equation eludes you, pick an unusual number for \(x\). Rates are in
\(\frac{rooms}{hr}\)Let \(x = 6\)
L's rate = \(\frac{1}{x}=\frac{1}{6}\)
L and J's combined rate =
\((\frac{1}{6}+\frac{1}{J})=\frac{1}{1}\)
J's rate: \(\frac{1}{J}=(\frac{1}{1} - \frac{1}{6}) = \frac{5}{6}\)
Work competed in 20 minutes = \(\frac{1}{3}\) hour?
\(RT= W\)In 20 minutes, J completes
\((\frac{5}{6}*\frac{1}{3}) =\frac{5}{18}\) of a room
Using x = 5, find the answer* that yields \(\frac{5}{18}\)
A. \(\frac{1}{3x}=\frac{1}{(3*6)}=\frac{1}{18}\) - NO
B. \(\frac{x}{(x-3)}=\frac{6}{(6-3}=\frac{6}{3}=2\) - NO
C. \(\frac{(x-1)}{3x}=\frac{(6-1)}{18}=\frac{5}{18}\) - MATCH
D. \(\frac{x}{(x-1)}=\frac{6}{(6-1)}=\frac{6}{5}\)- NO
E. \(\frac{(x-1)}{x}=\frac{(6-1)}{6}=\frac{5}{6}\) - NO
Answer C
*1) if your answer is a fraction, do not reduce it (your answer is based on an assigned value for x - don't depart from that value); and 2) with this method you have to check all the answer choices _________________
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