If it take person A 4 hours to wash a car and it take person B 2 hours to wash the same car, how long would it take them to wash the car together?
Can someone please help, and explain their answer?
2007-04-11 16:47:23 · 9 answers · asked by Kar Kar 1 in Science & Mathematics ➔ Mathematics
It's not 3 hours - in that time, person B could have washed one and a half cars by themselves, let alone with help.
Person B washes the car at twice the speed of Person A. That means, if Person A has only washed 1/3 of the car, Person B would have washed 2/3. 1/3 plus 2/3 = a whole car!
It takes Person B 2 hours to wash a whole car. It would take Person B just 2/3 of 2 hours to wash a whole car. That's 120*2/3 minutes, or 80 minutes: 1 hour, 20 minutes.
2007-04-11 16:53:42 · answer #1 · answered by The Oracle 6 · 0⤊ 0⤋
If it takes personA 4 hours to wash, then in one hour, she does 1/4 of the job. Person B does 1/2 the job in an hour.
So after one hour, when they work together, they have finished 1/2 + 1/4 = 3/4 of the job. So, it will take 4/3 of an hourOR one hour and twenty minutes.
2007-04-11 16:52:13 · answer #2 · answered by MathMark 3 · 0⤊ 0⤋
We assume a uniform work rate.
Key: Reduce everything to 1 hour.
Person A can do 1/4 of the work in 1 hour.
Person B can do 1/2 the work in 1 hour.
So 1/4 + 1/2 = 1/x,
since it takes them x hours to do the job working together.
So
1/4 + 1/2 = 1/4 + 2/4 = 3/4 = 1/x.
and x = 4/3 hr or 1 hr 20 min.
2007-04-11 16:53:57 · answer #3 · answered by steiner1745 7 · 0⤊ 0⤋
This is a normal beginning algebra problem.
First figure how many cars per hour one person can wash.
A 1 car per four hours or 1/4 car/hour
B 1 car per two hours or 1/2 car/hour
Working together they wash 1/2 + 1/4 cars per hour or:
3/4 car/hour
or in hours per car 4/3
2007-04-11 16:54:14 · answer #4 · answered by a simple man 6 · 0⤊ 0⤋
Cars washed in t hours = cars/hour x t time
For person A C(A) = 1/4 t
For person B C(B) = 1/2 t
For both C(A)+C(B) = 1/4 t + 1/2 t
For one car 1 = 1/4 t + 1/2 t
Together, they can do 3/4 car in 1 hour, so to do one car, it takes then 4/3 hours.
2007-04-11 16:55:13 · answer #5 · answered by cattbarf 7 · 0⤊ 0⤋
guy or woman A can paint a million abode/6 hours. guy or woman B can paint a million abode/4 hours the significant element is to apply the given suggestions and translate them into gadgets. as a results of fact its asking for the sum of those 2 expenditures you upload them at the same time : a million/6 + a million/4 = (4 + 6)/24 = 10/24 = 5 properties/12 hours. it truly is 5 properties for each 12 hours. for each hour it truly is 12 hours/5 properties = 2.4 hours or 2 hours and four-10th of an hour it truly is and extra (4/10) hour *(60 minutes/a million hour) = 4(6) = 24 minutes
2016-12-16 03:29:53 · answer #6 · answered by declue 4 · 0⤊ 0⤋
Since B will wash 2/3rd in 80 min, A in that same 80 min will wash the remaining 1/3rd.
2007-04-11 16:59:10 · answer #7 · answered by Anonymous · 0⤊ 0⤋
i think its impossible, because youre supposed to find the common factors but person B will always be ahead
2007-04-11 16:51:45 · answer #8 · answered by Anonymous · 0⤊ 2⤋
just half the times it takes ea. peep.
itll take 3 hrs.
2007-04-11 16:50:53 · answer #9 · answered by sweet_babe 2 · 0⤊ 3⤋