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A Photo scanner (A) can scan all the pictures in 2 hours and 15 minutes.
Together, scanner (A) and scanner (B) can do the same work for 1 hour and 9 minutes.
a. Which scanner is more effective?
b. How much faster does it get the work done?
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The rate of work of scanner (A) is a job per minute,
or 0.007407407 a job per minute.
The combined rate of work is a job per minute,
or 0.014492754 a job per minute.
Hence, rate of job of scanner (B) is 0.014492754 - 0.007407407 = 0.007085347 a job per minute.
Thus we see that the scanner (A) is more effective: its rate of work is higher.
Scanner (A) is = 1.04545437 = 1.045 (rounded) times as fast as scanner (B).
Solved.
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On the way, you learned a conception " rate of work ",
which is the basic in solving such problems.