Question

Check my answer? Calculating sums?

Answer 1

I got B

Answer 2

You can use the formula Sum a*r^n = a / ( 1 - r) , as long as |r | < 1

Answer 3

here 'a' is the first term

Answer 4

so we have to find the first term, we know r=.999

Answer 5

@perl I plugged in 1000 for a and got 1 million for the right side of the equation you listed

Answer 6

that formula works when you start from n = 0

since you're starting at n = 1, you have to subtract off the first term (because that term at n = 0 is not part of the summation)

Answer 7

so you have , n=1 is the first term
plug that in
1000( .999^1)

Answer 8

Sum = (1000*.999) / ( 1- .999)

Answer 9

That works too, you can make the first term 1000*.999

Answer 10

the nice thing about the formula, n can start at any number. 'a' just has to be the first term

Answer 11

Ooooh I get it. so its c @perl

Answer 12

correct

Answer 13

thank you so much @perl