Master and apprentice

Master painted the roof in 3 hours and apprenticed for 4 hours. How many roofs do they paint an hour, and how many in three-quarters of an hour?

Correct answer:

x =  7/12
y =  7/16

Step-by-step explanation:

$x=\frac{1}{3}+\frac{1}{4}=\frac{4}{12}+\frac{3}{12}=\frac{4+3}{12}=\frac{7}{12}=0.5833$

$y=\frac{3}{4}\cdot x=\frac{3}{4}\cdot \frac{7}{12}=\frac{3\cdot 7}{4\cdot 12}=\frac{21}{48}=\frac{7}{16}=0.4375$

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