Question

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Sue can shovel snow from her driveway in 65 minutes. Tom can do the same job in 45 minutes How long would a
take Sue and Tom to shovel the driveway if they worked together?

Answer 1

26.59 minutes

Explanation:

Let's say the time needed to do the driveway combined is x. Sue does y parts of the driveway, and Tom does z parts of the driveway. Combined, y + z = 100% = 1, as they finish the whole driveway.

Next, Tom will take 45 * z minutes to do his part of the driveway. For example, if he did 50% = 0.5 of the driveway, he would take 45 * 0.5 = 22.5 minutes to do it. Similarly, Sue will take 65 *y minutes to do her part of the driveway. Since they will finish at the same time, we can say

45 * z = 65 * y

y + z = 1

Therefore, if we subtract y from both sides of the second equation, we have

z = 1-y

We can then plug 1-y in for z in the first equation to get

45 * (1-y) = 65 * y

45 - 45*y = 65*y

add both sides by 45 * y to separate the y values and their coefficients

45 = 110 * y

divide both sides by 110 to find y

y = 45/110 = 0.409

Use 1-y=z to get z = 1-0.409 = 0.59

Therefore, 45*z = 26.59 = 65*y