Friday, September 10, 2010

Rates P6 2010 SA2 Rosyth P2 Q16

Machine A and B each printed a fixed number of newspaper per hour. Machine B started printing earlier at a rate of 75 copies per hour. After Machine B had printed for 10 hours, Machine A had printed 340 copies. After Machine B had printed for 16 hours, Machine A had printed 886 copies. (a) How many copies of newspaper did Machine A print per hour? (b) How long would Machine B have worked when both machines have printed a total of 2750 copies? [5 marks][Answer given: 91 copies, 20 hours]


B1: 10 h --> 10 x 75 = 750 copies
A1: ? h --> 340 copies

B2: 16 h --> 16 x 75 = 1200 copies
A2: ? + 6 h --> 886 copies

A: 6 h --> 886 - 340 = 546 copies
     1 h --> 546/6 = 91 copies

a) It was 91 copies.


A + B : 1 h --> 91 + 75 = 166 copies

2750 - 750 - 340 = 1660 copies

1660/166 = 10 h

10 + 10 = 20 h

b) It was 20 h.

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