Sheila can wash her car in 15 minutes. It takes Bob twice as long to wash the same car. How long does it take them to wash the car working together?
Now I looked at this equation and I got 15/60 For Sheila and 30/60 For Bob. What I don't get is how to put the equation together in the way they are asking. Explain how to put the equation together and how to solve it, use examples if you need to. Please keep it simple!
2007-04-28 04:22:17 · 7 answers · asked by babbaler 2 in Science & Mathematics ➔ Mathematics
Okay, will you please vote before you leave it would help a lot.
Thanks for the help guys I really needed a refreshment of rational expressions.
If you can please add more examples and explainations of rational equations to help me with my review!!
2007-04-28 04:45:07 · update #1
15 x 30 /15 + 30 = 450 / 45 = 10 minutes.
This is a shortcut I learned from being a math tutor for 7 years. It is based on cross products of adding fractions.
The way this is traditionally solved is :
Shiela can wash 1/15th car in 1 minute
Bob can wash 1/30th car in 1 minute
So 1/15 + 1/30 = 3/30 , so 1/10 of the car gets washed in 1 minute.
So it takes 10 minutes to wash the entire car.
2007-04-28 10:39:54 · answer #1 · answered by Don E Knows 6 · 0⤊ 0⤋
If Sheila and Bob wash the car together then you can figure half the time for each. Sheila would be half done in 7 1/2 min. Bob would be a quarter done in the same time. that leaves only 1/4 of the car. Sheila wold take 1 7/8 minutes more, and bob would take 3 3/4 minutes more. so add them up and you get 11 3/4 minutes. Maybe?
2007-04-28 04:34:38 · answer #2 · answered by magix151 7 · 0⤊ 1⤋
Sheila can wash 1 car per 15 min (1/15)
Bob can wash 1 car per 30 min (1/30)
together they are (1/15) + (1/30) = (2/30) +(1/30) = (3/30)
= (1/10) = 1car/10 minutes
it takes them 10 minutes
another way to look at it is since sheila is twice as fast as bob she has to do twice as much. so sheila does 2/3 of the car bob does 1/3. It takes sheila 2/3 of 15 min to do 2/3 the car.
2/3 of 15 = 10 min
2007-04-28 04:29:42 · answer #3 · answered by Nick 3 · 1⤊ 0⤋
All right, I think this is how it goes. You have to figure out how much of the car each of them can wash in one minute. That is to say, since Sheila can wash her car in 15 mins. then she can wash 1/15 of her car in one minute. Bob can therefore do 1/30 of the car per minute. You can then combine them by finding a common denominator. So, Sheila washes 2/30 of her car per minute, and Bob does 1/30 per minute, so together they are doing 3/30 of the car (or 1/10) per minute. They should finish washing the car in 10 minutes. I'm not sure, but it makes sense to me...hope it helps.
2007-04-28 04:37:43 · answer #4 · answered by Rob 1 · 0⤊ 0⤋
Bob is just going to slow Sheila down and its going to take both of them 22.5 min to wash the car. 45/2=22.5
2007-04-28 04:33:53 · answer #5 · answered by dwinbaycity 5 · 0⤊ 1⤋
In Australia you will be in big trouble if you waste water washing a car, only allowed to wash windows and lights and the water must be from a bucket
2007-04-28 04:30:58 · answer #6 · answered by wimafrobor 2 · 1⤊ 0⤋
that's inverse ratio so calculate artwork performed in unit time right here that's hour. via an entire artwork in 8 hr. so in a million hr it could pump a million/8 area of artwork. further B can Pump a million/B area of artwork the two certainly one of them completes a million/8 + a million/B area. a million/ 8 + a million/B = a million/5 a million/B = a million/5 – a million/8 = 3/40 area in a million hr so for a million finished artwork time = 40/3 hr = 13 a million/3 hr = sixteen hr 20 min -----
2016-10-14 00:11:11 · answer #7 · answered by ? 4 · 0⤊ 0⤋