Question

if sarah and tim work together use 4 hours to finish a project, tim use 6 hours to complete the project alone, how long will sarah finish project alone?

Answer 1

Answer:

She will finish in 12 hours.

Explanation:

∵ The time taken by Sarah and Tim when they work together = 4 hours,

∴ The one day work of both Sarah and Tim = $\frac{1}{4}$

Now, time taken by Tim when he works alone = 6 hours,

So, his one day work = $\frac{1}{6}$

Thus, the one day work of Sarah = Their combined work - one day work of Tim

$=\frac{1}{4}-\frac{1}{6}$

$=\frac{3-2}{12}$

$=\frac{1}{12}$

Hence, the time taken by Sarah when she works alone = $\frac{1}{\text{her one day work}}$

$=\frac{1}{1/12}$

= 12 days.