Basic Algebra/Working with Numbers/Formulas

Lesson

If a=5 and b=6 then the area is ab or 5×6=30.

In this lesson we will be learning formulas. A formula is a standard procedure for solving a class of mathematical problems

There are many different kinds of formulas and like it or not most of us high school kids need to know some of them.

To give you an example of a formula we will show you the formula for finding area.

To find the area of a rectangle you multiply the length times the width. If the rectangle on the right is five inches wide and six inches long you would multiply five times six and get thirty, that would be the area of this rectangle. That is the formula for the area of a rectangle: Length * Width.

Of course there are other harder formulas you will have to work with but now you know the basics of what a formula is.

A formula is an established form of words or symbols for use in a ceremony or procedure.

Example Problems

Example A:

Solve for 'y':

(a = 7)

a +5 + y = 20

Answer:

a + 5 + y = 20 (Put the 7 in place of the 'a')

7 + 5 + y = 20 (Add the integers, add 7+5=12)

12 + y = 20

12-12 + y = 20 - 12 (to get the 12 to the other side, add -12 to each side.)

y = 8 (20-12=8, so this leaves y=8)

Check:

a + 5 + y = 20 (to check it, put the 7 in place of the a, and the 8 in place of the y.)

7 + 5 + 8 = 20 (7+5+8=20, it's correct!)

Example B:

Solve for 'x':

(a = 7)

5 + 2 + x + a = 24

Answer:

5 + 2 + x + 7 = 24

14 + x = 24

14-14 + x = 24-14

x = 10

Check:

5 + 2 + x + a = 24

5 + 2 + 10 + 7 = 24

Practice Games

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Practice Problems

(Note: put answer in parentheses after each problem you write)