Question 1006902
On the nth day, Heather saves 2n dimes. In n days, she has a total of:


2 + 4 + ... + 2n
= 2(1 + 2 + ... + n)
= {{{2 * ((n)(n+1))/2}}}
= n(n+1) dimes.


We want to know how much money she has at the end of 30 days, so use n = 30.


# of dimes = 30(31) = 930
amount of money = $9.30