Question 37589
A principal of $5000 was invested in a savings account for 4 years.  If the interest earned for the period was $400, what was the interest rate?
{{{P(a)=a(1+r)^t}}} your equation for interest
{{{5400=5000(1+r)^4}}} where {{{P(a)}}} is final amount; {{{a}}} is initial amount; {{{r}}} is rate; and {{{t}}} is time
{{{(1.08)=(1+r)^4}}}
{{{1.0194=1+r}}}
{{{0.0194=r}}} the rate was about 1.94%
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Allen bought 20 stamps at the post office in 37¢ and 20¢ denominations.  If the total cost of the stamps was $7.06, how many 37¢ stamps did Allen buy?
define variables:
s=amount of 20¢
l=amount of 37¢
define equations:
s+l=20
0.2s+.37l=7.06
combine:
s=20-l
so....
0.2(20-l)+.37l=7.06
4-.2l+.37l=7.06
.17l=3.06
l=18 Allen bought eighteen 37¢ stamps.
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The perimeter of a rectangle is to be no greater than 300 in., and the length must be 125 in.  Find the maximum width of the rectangle.
perimeter<2(length)+2(width)
300>2(125)+2(w)
300>250+2w
50>2w
25>w the maximum width must be less than twenty five .... (if you only concidered integer values, than the value would be 24)
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One number is 8 less than another.  If 5 times the smaller number minus 2 times the larger number is 14, find the two numbers.
define variables:
l=larger number
s=smaller number
create equations:
l-8=s
5s-2l=14
combine:
s=l-8
so ....
5s-2l=14
5(l-8)+2l=14
5l-40+2l=14
3l=54
l=18
s=10