Every Sunday, Mary mows her lawn. It takes her 4 hours to finish mowing is she is working alone. This Sunday, however, Mary's friend Dominic said that he's help her. If together, they are able to mow the lawn in 2 hours and 24 minutes, how long would it take dominic to mow the lawn by himself?
2007-02-14 11:22:07 · 10 answers · asked by HopFropLeapCat 1 in Education & Reference ➔ Homework Help
It would take him 5 hours. Mary can do 25% of the lawn every hour. Dominic *we don't know yet. If I guess 5 hours that means he can do 20% every hour. Together they will do 45% in an hour. So 90% in two hours and 100% in 2.4 hours which is 2 hours and 24 minutes.
2007-02-14 11:32:35 · answer #1 · answered by Nelson_DeVon 7 · 0⤊ 0⤋
Well the question is how fast does HE work when he's alone not HER. WE already know that she mows the lawn in 4 hours. if he mowed the lawn in 4 hours when he was alone then together they'd mow it in 2 hours. It gets confusing because when they're together they get it done in 2 hours and 24 minutes...
ok so now I've explained why everyone else is wrong I'm stuck. I don't know how to figure it out either. You must have some crazy teacher... and I must have the same one because I have that same problem due friday... :(
well good luck!
EDIT: Nevermind... I think ^ that guy might be right... it makes sense after all...
2007-02-14 11:36:40 · answer #2 · answered by Anonymous · 0⤊ 0⤋
4 hours
2007-02-14 11:25:51 · answer #3 · answered by Anonymous · 0⤊ 1⤋
4 hours. Nothing suggests she works at a different rate when Dominic helps.
2007-02-14 11:30:23 · answer #4 · answered by Thirdeye 2 · 0⤊ 0⤋
4 hours 48 minutes by herself
2007-02-14 11:29:40 · answer #5 · answered by rui h 1 · 0⤊ 0⤋
Mary can mow .25 of the lawn in one hour; so Mary's rate is MR = .25L/1hr where L = 1 Lawn and hr = hours.
Dominic's rate is DR = xL/1hr, where x is unknown.
Now (MR + DR)*2.4hr = 1L
(.25L/1hr + xL/1hr)*2.4hr = 1L
the hours and lawns cancel, leaving
(.25 + x)*2.4 = 1
2.4x + 0.6 = 1
2.4x = 0.4
x = 0.167
Now since Dominic's rate was DR = xL/hr, we can say
xL/hr * yhr = 1L, where y is the number of hours we are trying to determine.
0.167L/hr * yhr = 1L
agian, hours and lawns cancel leaving
0.167y = 1
y = 5.99
It would take Dominic 5.99 hours to mow the lawn by himself.
Check:
(.25L/1hr + .167L/1hr)*2.4hr =
0.417L/hr * 2.4hr =
0.417L * 2.4 =
1.008L
There is trivial error from rounding.
2007-02-14 11:54:20 · answer #6 · answered by Spookius Mortem 3 · 0⤊ 0⤋
4 hours and 24 minutes. I hope that helps!!
2007-02-14 11:25:23 · answer #7 · answered by Anonymous · 0⤊ 0⤋
2.24X2= 4 hours and 48 minutes. I hope I'm right.
2007-02-14 11:27:13 · answer #8 · answered by danity56 2 · 0⤊ 0⤋
4 hr and 48 minutes
.
2007-02-14 11:25:19 · answer #9 · answered by Heyhey 5 · 0⤊ 0⤋
how is he helping her? does he bring his own lawnmower over or is he just using hers? i'm confused.
do they both push on the same mower?
2007-02-14 11:30:56 · answer #10 · answered by Anonymous · 0⤊ 0⤋