When both printers H and J are used, a collection of books can be printed in 4 hours. While printing, Printer H broke down. As a result, it took 6 hours to complete printing. If it would take Printer J 12 hours to print the collection alone,
- How long would it take to print the collection of books using only Printer H? Express your answer in hours.
- How long was Printer H used before it broke down? Express your answer in hours.
(a)
Time taken by Printer H and J:
4 h → 1 collection of books
1 h → 1 ÷ 4 =
14 collection of books
Time taken by only Printer J:
12 h → 1 collection of books
1 h → 1 ÷ 12 =
112 collection of books
Time taken by only Printer H:
1 h →
14 -
112 =
16 collection of books
1 collection of books → 1 ÷
16 = 1 x 6 = 6 h
(b)
Time taken by only Printer J:
6 h → 6 x
112 =
12 collection of books
Fraction of the collection of books to be done by Printer H
= 1 -
12=
12 Time taken by Printer H before it broke down:
12 collection of books →
12 ÷
14 =
12 x
41 = 2 h
Answer(s): (a) 6 h; (b) 2 h