Phone Math

The last couple months my sister has been calling me periodically to help with college algebra.(Why she is doing the class is another story.) We have done several lessons over the phone. Two nights ago she texted me at 11pm and asked me for help for the final time. I successfully explained how to deal with negative exponents, and then she asked me the next question.

If you have a saving account with 6.25% interest that compounds quarterly. You’re trying to save to have $4500 in two years how much money do you need to start with?

I was like, “I dunno. About four grand.”

She laughed and said she couldn’t really put that. I told her that if I had choices I could figure out which was right, but I didn’t know how to go back and come up with the number. (And I was already in bed.)

The next morning I woke up and had a text from her that read: $3955.56.

Damn. I’m good.