## Wednesday, May 26, 2010

### Thrift

Continuing our elementary education in money-related math terms, today we come to the word Thrift.

As I explained yesterday, the educational framework in California and most other states requires that we teach kids to live as responsible citizens of society. That means in the classroom we do not recommend "Eat, Drink and Be Merry, for tomorrow you die" as a guiding philosophy.

We are expected to have a more responsible attitude. We are positively required to teach Thrift, which means "restrained or disciplined spending habits" and "wise management of money and resources."

The dictionary suggests that being thrifty means "thriving by industry (work) and frugality, which leads to prosperity". Notice that we are in California, not Scotland. At the moment, it's hard to say this approach is working for our state's finances!

Back to the classroom:

We practice calculating unit pricing - here's a typical problem from our 6th grade book:

One store has apples for \$.79 per pound. A second stores has apples for \$1.50 per kilo. A third store sells apples for 25¢ apiece. Which is the best price per apple?

We point out that the best unit price doesn't always mean the best deal for the customer, especially with perishable goods. You might throw food away because it spoiled before you could eat it. But let's say you were eating out, and you need to calculate the bill with a tip. Excel Math is here to help:

Rami and her friend had a lunch bill that came to \$22.50. Rami paid the bill plus a 20% tip for the waiter. How much money did she pay?

We explore many facets of wise shopping - comparing prices, calculating the unit price, applying discounts, understanding sales taxes, tipping on a dinner check, etc. We must respect both being a laborer and being management, so we don't quibble about whether to tip the server 10%, 15% or 20% on lunch!

Ian deposited \$170 in a bank account that pays 5% annual interest. How much interest did he earn after one year?

We provide a basic overview of savings accounts, and interest paid on deposits. When I wrote this problem 4-5 years ago, I thought that 5% was a pretty low interest rate. Now I'd like to find a bank that would pay me so much!

We also tackle foreign exchange rates, a great math subject! Here's a fairly recent problem (but today the exchange is 1.43):

One British pound equals 1.87 US dollars. How much money in US dollars would you receive in exchange for 8 pounds?

If you never learned to do these calculations in school, you could pick up a copy of 6th grade Excel Math and teach yourself how to be thrifty. Let's end with a complicated problem:

4 oz for 16¢                       2 lbs for \$1.44                6 ounces for 30¢

Here are the prices for a certain product. If you want one pound of this item, how much money will you have to spend if you chose the cheapest option?