<p>On the March SAT I had a problem like this and I didnt get how to do it.</p>
<p>Four workers can dig a 40-foot well in 4 days. How long would it take for 8 workers to dig a 60-foot well? Assume that these 8 workers work at the same pace as the 4 workers.</p>
<p>Is the asnswer 3?</p>
<p>Four workers can dig a 40 foot well in 4 days.
Having more workers will expedite the process. Common sense.
Therefore, double the worker and ceteris paribus = double the progress.
8 workers, then, can dig a 80 foot well in 4 days.</p>
<p>Now set up an equation</p>
<p>(80 foot) / (4 d) = (60 foot) / (x d)
Solve for x. Cross multiply and you get x = 3.</p>
<p>Thoughts: I think this is using common sense too much… Sorry if my approach confused you or anything.</p>
<p>This may help you to understand the problem better:
One person per day can dig: 40/(4x4) = 2.5 feet
Eight people per day can dig: 8X2.5 = 20 feet
60 feet would take 8 people: 60/20 = 3 days</p>
<p>This problem is d=rt problem. First you find rate of the four workers: d=rt, 40=4r, r=10ft/day. Then you setup a porportion: 4/10=8/x, x= 20ft/day(this is the rate for the 8 workers). Finaly, just plug the 20 into d=rt for the 8 workers. 60=20t, t=3</p>