4Tests Forums

ForumsHigh School Life • algebra Post ReplySend to a Friend
Author Topic
colonel000Posted - 30 July 2001 20:16  Show Profile
how can i solve this?
A and B can build a wall in 24 hrs. After A worked 7 hrs, B helped A and both together finished the rest of the work in 20 hours. ¿How long does it takes to each one to make the work?
DimaMedvedev Posted - 12 September 2001 19:40  Show Profile
Hi there. Well... this reply is kinda late now... But if you need help with Algebra, Physics, or Chemistry, please message me, and I will be very happy to help you... You see, I am a Junior in High School and I am already taking AP Statistics and AP Calculus, so I am sure I could solve any of your algebra problems. Here''s the solution for this one:

Let x be the speed (work per hour) at which worker A does his job, y - the speed at which worker B does his. 24x+24y=27x+20y , because as u said, both of them working together finish in 24 hours, and for the right side of the equation, both work together for 20 hours, after worker A has worked for 7 hours. (20+7=27). Simplify the equation above to get 3x=4y, divide both sides by 3 to get X=4/3*y
That means that worker A works faster than worker B, and it takes him only 3 hours to do the work that B does in 4 hours. Now you can substitute 4/3y in for x in any side of the equation. For example, 27x+20y=27*(4/3y)+20y=36y+20y=56y. That means that it will take 56 hours for worker B to build a wall or whatever it was at a speed Y. Now replace Y with 3/4x to get:
27x+20y=27x+20(3/4x)=27x+15x=42x Which means it takes 42 hours for the worker A to do his job. I hope that''s what the question asked. You dont have to use 27x+20y, you could use 24x+24y to get the same results. SOrry that I am reading your post only now, months later, but I will be willing to help you in the future.
Best regards,
Dima.
PS. My e-mail address is bearalex777@hotmail.com Anyone is welcome with math or science questions! See ya

godsdiamond Posted - 24 June 2006 12:57  Show Profile
Do you think that you could help me with some Algebra! And maybe helping me with comprehending some of the Science problems? It would be such a great help!

Thanx

Show All Forums | Post Reply