You are not logged in.
#1 2005-12-07 04:37:06
- Bobba_Jim
- Novice
Offline
Help with percentages
Hi All,
I have a mathematical problemt hat I just can't work out so I figured I'd put out there and see if anyone can help. I need a formula for the following situation:
---
Bob works 7 hours a day dealing with completed questionnaires posted to him.
Most questionnaires are easy to deal with and take him 10 minutes to deal with.
But if a questionnaire needs special attention it takes Bob 30 minutes to deal with it.
Assuming that only 20% of questionnaires need special attention, how many questionnaires can Bob deal with on 1 day?
---
My brain cannot deal with this problem, but I'm hoping I have provided all the neccessary information for a solution. Never was any good with percentages.
Hope someone has fun working it out or can point me in the right direction!
#2 2005-12-07 05:23:10
- mathsyperson
- Moderator
Offline
Re: Help with percentages
We need to work out the average time that Bob would take to deal with a questionnaire.
80% of them are short and he takes 10 minutes, so we do 80%/100% * 10 minutes = 8 minutes.
The other 20% are long and take 30 minutes, so we do 20%/100% * 30 minutes = 6 minutes.
Add these to get the total average time and we get 14 minutes.
He works for 7 hours, which is 420 minutes.
Therefore, he can deal with 420/14 = 30 questionnaires in 1 day.
Why did the vector cross the road?
It wanted to be normal.
#3 2005-12-07 09:23:44
- MathsIsFun
- Administrator
Offline
Re: Help with percentages
And backwards:
He has 30 questionnaires. 24 (ie 80%) take 10 mins, and 6 (ie 20%) take 30 mins. 24×10 + 6×30 = 420 mins = 7 hrs.
"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman
#4 2005-12-07 09:52:29
- irspow
- Power Member
Offline
Re: Help with percentages
I will come late on this one also. Different strokes for different folks. I like to do these types of things algebraically.
7 hours = 420 minutes
special questionaires = .2 q (q=any questionaire)
simple questionaires = .8 q
total time = .8q(10 minutes) + .2q(30 minutes)
420 = .8q(10) + .2q(30)
420 = q(8 + 6)
q = 420/14 = 30
The average concept used by mathsyperson never even occured to me. Go figure.
#5 2005-12-07 10:47:17
- mathsyperson
- Moderator
Offline
Re: Help with percentages
It's pretty much the same method though, I was just explaining it in a simpler way.
Why did the vector cross the road?
It wanted to be normal.
