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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