ralanko wrote:
A worker can load 1 full truck in 6 hours. A second worker can load the same truck in 7 hours. If both workers load one truck simultaneously while maintaining their constant rates, approximately how long, in hours, will it take them to fill 1 truck?
A. 0.15
B. 0.31
C. 2.47
D. 3.23
E. 3.25
One approach is to
assign a nice value to the entire job (of filling a truck)
We want a number that works well with the given times (6 hours and 7 hours)
42 is such a number.
So, let's say that filling the truck is equivalent to shoveling 42 scoops of dirt into it.
A worker (we'll call worker A) can load 1 full truck in 6 hoursRate = output/time = 42 scoops/6 hours = 7 scoops/hour
So, worker
A's RATE is 7 scoops/hourWorker B) can load 1 full truck in 7 hoursRate = output/time = 42 scoops/7 hours = 6 scoops/hour
So, worker
B's RATE is 6 scoops/hourSo, their COMBINED rate =
7 scoops/hour +
6 scoops/hour =
13 scoops/hourWorker B) Approximately how long, in hours, will it take them to fill 1 truck?Time = output/rate
= 42 scoops/
13 scoops/hour= 42/13 hours
= 3 3/13 hours
ASIDE: Notice that 3 3/12 hours = 3.25 hours
So, 3 3/13 hours will equal a
little less than 3.25 hours Answer: D
Cheers,
Brent
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