+1633 Find the sum of 1−12+15−110+125−150+1125−1250+⋯+1510−12⋅510.
The answer should be in the form of a decimal rounded to the nearest HUNDREDTH.
I think this problem is looking for a few equations related to the sequence, but not sure which ones. Thanks :/
+118696
1−12+15−110+125−150+1125−1250+⋯+1510−12⋅510=1+15+125+1125+⋯+1510−12−110−150−1250+⋯−12⋅510
the first line is the sum of a GP a=1, r=1/5 11 terms
the second is the sum of a GP a=-1/2, r=1/5 11 terms (that dot is a times sign not a decimal point)
Work them out and add them together.
+1633 Thanks for the initial step Melody.
So for the first line I got 1.2499999744.
Then subtracting from the first line with the second line I got very close guess. Instead of subtracting everything else. I got to 0.6250015744, and I knew rounding to the nearest hundredth would get me 0.63 or 0.62.
With your strategy, I got 0.62 as the nearest hundredth.
