Couple Problems I don't seem to be able to solve

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I have a few problems that I encountered today that I don't seem to be able to solve. Please help me out.

#1
In the arithmetic sequence t1, t2, t3, ..., tn,..., t1 = 23 and tn = tn-1 - 3 for every n>1. What is the value of n, when tn = -4?

#2
The perimeter of square region S and rectangular R are equal. If the sides of R are in the ratio 2:3 what is the ratio of the area of Region R to the Region S?

#3
Two Water pumps working simultaneously at their respective rates, took exactly 4 hours to fill a certain swimming pool. If the constant rate of one pump was 1.5 times the constant rate of the other, how many hours would it have taken the faster pump to fill the pool if it had worked alone at its constant rate?

#4
In a stack of boards at a lumber yard, the 20th board counting from the top of the stack is immediately below the 16th board counting from the bottom of the stack. How many boards are in the stack?
I always get 36 but it should be 34?

#5
For which of the following functions F(a+b) = f(a) + f(b)?
Answer: F(x) = -3x????

#6
Adam and Beth each drove from Smallville to Crown City by different routes. Adam drove an average of 40 miles per hour and completed the trip in 30 minutes. Beth' route was miles longer and it took her 20 minutes more than Adam to complete her trip. How many miles per hour did Beth drive on average?

Thanks everyone!
Last edited by RickH on Sun Aug 15, 2010 4:15 pm, edited 2 times in total.
Source: — Problem Solving |

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by RickH » Sun Aug 15, 2010 4:14 pm
I just realized something for my last questions on #6:

Since the time is given in minutes, but the speed is on miles PER HOUR, I would need to set everything up in hours correct?

Meaning like this:

0.5 = Distance/40
20 = Distance

Beth would then be the following:

5/6 = 25/S
5/6S = 25
S = 30

Which would be the correct answer. I always got 24 because I calculated with, what I now realize to be 30 HOURS instead of 30 MINUTES. :oops:

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by Gurpinder » Sun Aug 15, 2010 5:39 pm
Could you please post EACH question as a separate post!
"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.

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by RickH » Sun Aug 15, 2010 7:06 pm
Sure thing.

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by Gurpinder » Sun Aug 15, 2010 7:11 pm
RickH wrote:Sure thing.
Thank you!
"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.