Two motor mechanics, Raju and Siraj, working together can overhaul a scooter in $6$ hours. Raju alone can do the job in $15$ hours. In how many hours can Siraj alone do it?

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Solution

We know that,
Number of hours raju requires to do the job $= 15$ hours
Let us consider the number of scooters siraj overhauls in an hour to be $x$ , then

Work done by both raju and sriraj in $1$ hour $= 1 / 15 + 1 / x = (x + 15) / 15 x$

$(x + 15 / 15 x) = 1 / 6$ [As they both can finish the job in $6$ hours]
$6 x + 90 = 15 x$
$9 x = 90$
$x = 90 / 9$
$x = 10$

$∴$ siraj can do the work in $10$ hours.

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Two motor mechanics, Raju and Siraj, working together can overhaul a scooter in 6 hours. Raju alone can do the job in 15 hours. In how many hours can Siraj alone do it?

Two motor mechanics, Raju and Siraj, working together can overhaul a scooter in $6$ hours. Raju alone can do the job in $15$ hours. In how many hours can Siraj alone do it?