Jim's Math Corner
by James W. Leonardi
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Middle School |
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Portions, Bases, Rates |
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Portions, Bases, and Rates
Portion is the product of the base and rate (in two place decimal form when money is involved).
P = BR
Base is the ratio of the portion to the rate (in two place decimal form when money is involved).
B = P/R
R is found using a proportion.
R/100 = P/B
For example: Some clothing was regularly priced at $550. If it was on sale for 40% off, what was the selling price?
One way: $550 was the original price, that would be the base (B). Of course 40% is the rate (R). Since we have the base and rate, we must be looking for the portion (P). Don't forget to change the 40% to a decimal (0.4).
P = BR = $550(0.4) = $220 the discounted amount
SP(sales price) = B - P = $550 - $220 = $330
Second way: Since we get 40% off the original price, we must be paying 60% of the original price.
SP = $550(0.6) = $330
1. We must determine what we are to find --- portion, base, or rate.
2. We must determine what we have either portion and base, portion and rate, or base and rate.
3. We must use the correct formula.
This should help those who just needed a review or a jump start for the "A" student. If you are like most of us, you will need a more in-depth study and more examples. I have kept the price down so everyone who needs help can afford it. For more in-depth FREE help download this file (in word 97 format).