Jack and Jill wash a car at the same rate . Working together it takes them an hour and 10 minutes to wash a car. One day jack started washing a car by himself at 2:30 p m. When he was half way done , Jill joined him . What time did they finish washing the car?

Answer 1

It would take them 70 minutes to wash the whole car working together, working at the same rate.

Jack did half the car by himself , and that would have taken him 70 minutes working alone

so that leaves half the car to be washed by both working together.
This will obviously take them 35 minutes.

so add 70 min + 35 min to 2:30 ----> 4:15 pm