Learning Resources

Focus C: Population Growth

Suppose a jacket that you bought last year for $100 has gone up in price 10%. What is the cost now? I know you all quickly realize that it is $110. The question is, how do we arrive at the answer of $110? We don't simply take 10% of $100 and say the answer is $10. This makes no sense. It's not 10% of $100 that we actually want. It is 110% of 100 that we need to find, the answer to which is $110. Now some of you are saying, "yes, but I could have found 10% of $100 and added the answer of $10 to the original cost." While this is correct, it is quicker just to find 110% of $100. It's the same idea as when you are shopping for say a pair of jeans and want to quickly know the cost, including taxes. You can simply multiply the price of the jeans by 1.15. This will give you the total cost of the jeans.