Question

A takes 40 min. to do a job.b takes 1 hour to do the same job.A,B,and C start working together and the complete the work in 15 min. only.if C stands alone how much time is needed byC to complete that job

Answer 1

Let 1/A = 1/40
and 1/B = 1/60
and 1/A + 1/B + 1/C = 1/15

Add equation 1 and 2
1/A + 1/B = 5 / 120 = 1 /24

Subtract it from equation 3
1/C = 1/24 - 1 /15 = 1 / 40
C = 40 minutes

Please mark brainliest or thanks if it helped you :D