Please help me with this simple algebric quetsion!!!?

Question

we have a test on monday, on this and im kinda lost, this is one of our study guide questions, how do you solve it using A=P(1+r/n)nt -----------------------------nt are exponents!!!!!




okay, Joe had investments at 2 banks. the rates were 7.5% and 9%. the amt. invested at .5% was $300.00 less than the amt. invested at 9%. the total interset for the 1st year was 1586.25. How much was invested at each rate???


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-she gave us the answer
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x=2500
3x=7500
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so i know the answers but i dont know how to get it!!!thanks!

Answer 1

good luck!

Answer 2

The formula you gave us, which is for compound interest, does not apply here. What you have here is a system of linear equations, one equation for amounts invested and one for interest. Let x be the amount at 7.5%, y the amount at 9%. So

y - x = 300 and
0.075x + 0.09y = 1586.25

Let's multiply the 1st equation by 0.075 and commute the x and y terms. Then we have

-0.075x + 0.075y = 22.50
+0.075x + 0.09y = 1586.25 ...... so we just add and get

0.165y = 1608.75
y = 9750
x = 9450

Now where did you get x = 2500, and where did 3x come in? I believe you've garbled together at least 3 different problems.

Answer 3

thats not simple algebra, thats calculus. and its:

A=P(1+r/m)mt

A = amount in an account at the time (balance)
P = initial amount/value
R = rate of interest (return) usually written as a decimal
M = # of compoundings each year (12 months in your case)
T = time in years

just plug in the numbers. that should help you out. I copied my notes for that formula

and the answer is just:
x=2500

because 3x=7500 equals 2500 when 7500 is divided by 3

Answer 4

if you say it's simple then why do you need help?


wish i could help...but math was never my best subject.

Answer 5

x=2500