Two persons A and B working separately can sanitise a building in 6 and 10 hours, respectively. They work in stretches of one hour alternately. If A begins at 8 a.m., then when will the work be finished?
Answer & explanation
Correct answer: option 2
A = 6 hours, B = 10 hours
⇒Working on alternate hours, starting with A at 8 am,
1st hour = 5 units
2nd hour = 3 units
Every 2 hours = 8 units
⇒Hence, in 6 hrs, 24 units of work will be completed.
and in 7 hrs, 29 units of work will be completed.
⇒The remaining work i.e; 1 unit will be completed by B in = \(\frac{1}{3}\)hours.
Therefore, The Total hours taken to complete work = 7 + \(\frac{1}{3}\) =
\( { 7}_{3 }^{1 } \) hours.