Posted by Mat on Wednesday, July 30, 2014 at 6:42pm.
1.A father can do a job in a certain number of hours. His son takes twice as long to do the job. Working together, they can do the job in 6 hours. How many hours does it take the father to do the job alone?
3.David is 5 years older than Paul. In 5 years, David will be twice as old as Paul is now. How old is David now?
this is what i have so far:
2D+p(i'm not sure if this is right)
- math - bobpursley, Wednesday, July 30, 2014 at 8:47pm
combined rate=1/F +.5/F=1.5/F=1/6
subtract second equation from first
-10=-P P is 10 now, so D is 15
- math - Reiny, Wednesday, July 30, 2014 at 9:01pm
job/rate = time --> rate = job/time
let the fathers rate = job/x
let the son's rate be job/2x
combined rate =job/x + job/2x
combined time = job ÷(3job/2x)
= job (2x/3job)
but 2x/3 = 6
2x = 18
x = 9
It would take 9 hrs for the father to work alone
Paul's age --- x
David's age -- x+5
in 5 years:
David --> x+10
x+10 = 2x
x = 10
Paul is now 10 and David is now 15
Answer This Question
More Related Questions
- math - A father can do a job in a certain number of hours. His son takes twice ...
- Math - Barry can do a certain job in 3 hours, whereas it takes Sanchez 5 hours ...
- elementary and intermediate algebra - Barry can do a certain job in 9 hours, ...
- math - Alex takes 3 hours longer to complete a certain job than Barry does. If ...
- math - A father can do a job as fast as two sons working together. If one sone ...
- math - 8 workers together at the same rate finished a painting job in 5 hours. ...
- math - 1.a collection of 105 coins consists of 1 peso and 5 pesos. if the total ...
- College Algebra - It takes Todd 3 hours longer than Tom to paint a 4x5 feet ...
- math - if you do a job in 4 hours, and your friend can do the same job but in 6 ...
- Word Problem - Martha can rake the leaves in her yard in 2 hours. Her brother ...