When both Machines P and Q are used, a book can be printed in 5 hours. When printing a book, Machine P broke down. As a result, it took 7 hours to complete the printing of the book. If it would take Machine Q 8 hours 20 minutes to print the book alone, (a) how long was Machine P used before it broke down? (b) how long would it take to print the book using only Machine P? [4 marks][Answer given: 2 hours before, 12½ h]
Q : 8 1/3 h --> 1 book
7 h --> 7 x 3/25 = 21/25 book
5 h --> 5 x 3/25 = 3/5 book
1 - 21/25 = 4/25 book
1 - 3/5 = 2/5 book
P : 2/5 book --> 5 h
4/25 book --> 4/25 x 5/2 x 5 = 2 h
1 book --> 5/2 x 5 = 12 1/2 h
a) It was 2 h.
b) It was 12 1/2 h.
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