Robert C. answered • 09/24/12
Dr. Robert can help you with Math and Science
Hi Stacey,
The way you have typed the problem, I am not sure which part is the exponent. I suggest that you use the caret (^) symbol to indicate the exponent. For example, if you mean e to the -420 power, you would put e^-420. Is that what you are going for?
Perhaps you could clarify your question with a comment.
Good luck,
Robert
Robert C.
Very good Stacey. That makes it much more clear to me. Now this becomes a simple issue of the order of operations. PEMDAS is a good reminder of which operations to do first: Parentheses, Exponents, Multiplication and Division, and Addition and Subtraction. Things inside parentheses are first.
1-(1-.081/12)^-420
Look inside those parentheses. I see a subtraction and a division. PEMDAS tells us to do the division first. (Make sure there isn't a missing set of parentheses from the problem. Sometimes things are presented as fractions with a numerator with many terms. In that case, you have to put all those terms in parentheses or it only looks like a single thing is on the topo of the fraction).
The division is 0.081/12, which is 0.00675, so our problem is now
1-(1-0.00675)^-420
Do the subtraction inside the parentheses.
1-(.99325)^-420
or just
1-.99325^-420
Now, with the things inside the parentheses handled, we have a subtraction and an exponent. Exponents come first. Keep in mind that a negative exponent is just the same as positive exponent but you take the answer and divide one by it.
A^-1 = 1/A
So we have
1-(.99325)^-420
or
1-1/((.99325)^420)
Plugging either into a calculator you get
1 - 17.1949 (rounded off)
-16.1949
This problem can be a bit tricker if you need to keep everything in fractional notation. In that case, remember that .081 is 81/1000, and follow basically the same strategy. Good luck.
09/24/12
Stacey R.
Sorry I put e to say that -420 is the exponent...e really isn't in the equation
09/24/12