+1993 What is the sum of the first eight terms of the series?
(−500)+(−100)+(−20)+(−4)+(−0.8)+...
Round the answer to two decimal places if necessary.
−996.09
−625
−624.99
−623
Wouldn't it be -625 rounded to the 2 decimal places?
+128401 The common ratio is -100/-500 = 1/5 = r
The sum, S, of the first n terms is given by
S = first term [ 1 - common ratio ^(n - 1) ] / [ 1 - r ]
So...the sum of the first 8 terms is
S = (-500) [ 1 - (1/5)^(8 - 1) ] / [ 1 - 1/5] =
(- 500 ) [ 1 - (1/5)^7 ] / [ (4/5) ] = -624.992
Rounding to 2 decimal places.....note that the third decimal place is < 5
So....we round to -624.99
