Question

Linndsey and stephen work at a factory. lindsey can complete on full job in 3 hours, and stephen can complete the same job in 5 hours. if lindsey and steophen work together on the job for 1 hour, then how long, in minutes, wil it take stephen to finish the job by himself?

Answer 1

Solution: Linndsey's 1 hour work $=\frac{1}{3}$

Stephen's 1 hour work $=\frac{1}{5}$

Linndsey's and Stephen's work together for 1 hour $=\frac{1}{3} +\frac{1}{5} =\frac{8}{15}$

Therefore, the amount of work done in 1 hour by both Linndsey's and Stephen's is $\frac{8}{15}$

Now the amount of Job left is $1-\frac{8}{15}=\frac{7}{15}$

Let t be the amount of time Stephen takes to do the remaining job of $\frac{7}{15}$

$\therefore \frac{1}{5} \times t = \frac{7}{15}$

                        $t=\frac{35}{15} =\frac{7}{3}$ hours

Now let's convert hours into minutes as :

$\frac{7}{3}\times 60 = 140$ minutes

Therefore, it will take 140 minutes to Stephen to finish the job by himself.