Question

A and B working separately can row a field in 12 and 15 hours respectively they work alternately each for an hour with the beginning at 5:00 a.m. at what time the rowing will be completed?​

Answer 1

Answer:

13 hours and 15n minutes

Answer 2

Answer:

A and B will complete rowing the field by 6:15 pm

Step-by-step explanation:

given, A can row the field in 12 hours and B can complete the same work in 15 hours

to find: the time taken to row the field, if they work alternatively, starting at 5 am

LCM of 12 and 15 is 60

so, A can do 5 units/hour,starting the work at 5 am

and, B can do 4 units/hour, starting the work at 6 am

by 9 am, A and B together will complete 5+4 = 9 units

number of cycles = $\frac{60}{9}$

        = 6 cycles of 2 hours each and 6 units left

in the remaining 6 units, 5 units will be done by A in 1 hour and 1 unit will be done by B in $\frac{1}{4}$ hour

total time required to complete the work = (6×2) + 1 + $\frac{1}{4}$

          = 13 hours 15 minutes

thus, if A and B started rowing the field at 5 am, it will take 13 hours 15 minutes to complete the work

that is , A and B will complete rowing the field by 6:15 pm