1. Sec 3.3 Finding Base Objectives –Use the basic percent formula to solve for base. –Find the amount of sales when taxes and rate of taxes are known. –Find the amount of an investment when expense and rate of expense are known.

2. Reminder The Basic Percent Formula Part = Base x Rate P = B x R Can we define B in terms of P and R?

3. P = B x R, then B x R = P

4. Dividing both sides by R, we have:

5. Re-Grouping the terms, we have:

6. Any number divided by itself yields 1:

7. Any number times one is that number:

8. We can use a mnemonic device to remember that:

9. Example 1 23 marbles is 0.5% of _______ marbles. 23 is 0.5% of _____. 23 = 0.5% x ______.

10. Example 1 23 = 0.005 x _______ P = R x B

11. Homework Sec. 3.3 2, 4, 6, 8, 10,... 36 Homework Sec. 3.3, Supplementary Exercises 2, 4, 6, 8, 10, 12, 14