Question

1+2+4+8+...+128

Answer 1

143... just add this up

Answer 2

its 143

Answer 3

yea...

Answer 4

it is a geometry series. use this formula :
Sn = a (r^n - 1)/(r - 1)

first you have to find n, just use the formula to find nth term :
an = a * r^(n-1)
here known that an = 128, r(ratio) = 2
so,
128 = 1 * (2)^(n-1)
2^7 = 2^(n-1)
7 = n - 1
n = 8

Answer 5

now plug in all values a = 1, n = 8 and r = 2 into formula :
Sn = a * (r^n - 1)/(r - 1)
so,
S8 = 1 * (2^8 - 1)/(2-1) = .... ????

Answer 6

@shadow22 and @homeschoolgal, didnt you guys see the series is :
1 + 2 + 4 + 8 + ... + 64 + 128

look that the 2 lats term are 64 and 128, where thy has sum 192, impossible get 143 :v