Problem Math?

Question

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?

Answer 1

if this is simple interest then
400/4 = $100 per year.
100/5000 * 100 = 2% per year.

Now in real life interest is compounded. That is you earn interest the first year, it is added to the principle then interst is calculated on the new amount the following year, and so on, every subsequent year. for this you have to use this formula:

P+I = P (1+i)^n
P=principal
I= amount of interest earned
i= interest rate (in decimal form)
n= number of years invested

5400 = 5000 (1+i)^4

5400/5000 = (1+i)^4

Ln (54/50) = 4 Ln (1+i)
Ln (1+i) = .01924
1+i = e^(0.01924)
i = 1.01942 - 1
i = .01942 *100% = 1.942 % per year

note the compounded rate is always slightly less than the simple rate.

Answer 2

I=PRT
400=5000*R*4
R=(400)/(5000*4)=(100/5000)=1/50=2 %

Answer 3

a million. So Gerhart pays 3.ninety 5, a million.40 5, and a million.10, for a entire of 6.50. to discover the share that the tip is, you divide the tip by utilising the fee of the food. a million.30/6.50 =.2, or 20%. 2. If the tip is eighteen% of the invoice, meaning that 6.40 8/X(the completed invoice) = .18 in case you go multiply, you get that 6.40 8/.18 = X, so X, the completed invoice, is 36 money. 3. 5.ninety 5 + 2.40 5 = 8.40 for the food. 20 % of the food is a million.sixty 8, so now the completed is 10.08 for the food and the tip. The revenues tax = 8.4 situations .05, which equals .40 two. subsequently, the completed that she pays is 10.08+.40 two=10.50. wish this helps!