Thread: nth partial sum of a geometric sequence

I don't even know if this is an nth partial sum of a geometric sequence problem but...
if someone wanted to save money to buy a used car and they saved $100 on the first day, then $75 on the second day, then $56.25 on the third day, how much will they have saved on the seventh day?
In 20 days, will they have enough to afford a used car that costs $500?
what would be the total amount they saved in that time?

thanks

Originally Posted by Intsecxtanx

I don't even know if this is an nth partial sum of a geometric sequence problem but...
if someone wanted to save money to buy a used car and they saved $100 on the first day, then $75 on the second day, then $56.25 on the third day, how much will they have saved on the seventh day?
In 20 days, will they have enough to afford a used car that costs $500?
what would be the total amount they saved in that time?

thanks

HI

This is a geometric sequence with a=100 , and r =0.75

On the 7th day , they will save

In 20days , they would have saved (in total)



Calculate this and if see whther its > or < 500 .