   SEARCH HOME Math Central Quandaries & Queries  Question from Kelly, a student: Hello! I know you might be thinking that I didn't look through your previous answers, but I really did. Here's my dilemma- I have a percent increase equation that is missing the 'old" value. I know that $65.09 is 70% greater than the average price, but I do not know the average price. How do I go about finding that? I tried to set up an equation, but its throwing me off because the unknown variable is in there twice, and it's been a long time since I've taken math Thank you for your help...greatly! Kelly, You said I know that$65.09 is 70% greater than the average price

I let a be the average price in dollars then I see in the statement above as

a plus 70% of a is $65.09 or a + 0.70 a = 65.09. On the left side a is a common factor so a(1 + 0.70) = 65.09 or 1.70 a = 65.09. Dividing both sides by 1.70 gives a = 65.09/1.70 =$38.28.

I hope this helps,
Penny     Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.