Adult Education Lesson Skill 22

1. Skill #22 Evaluating an Algebraic Expression
page 121 to 126 in your book
This is a classic type of algebra problem where you are given an algebraic expression
such as 3x + 7y2 and told to evaluate the expression if some numbers (made up by the
problem maker) are assigned to x and y. Let’s evaluate this expression if x = 4 and y = -1.
3x + 7y2
3(4) + 7(-1)2
12 + 7 (1)
12 + 7
19
I used the order of operations
(PEMDAS)

2. Look at page 121. The first example is easy.
Look at the next example. It is more like what I expect you to see on the GED.
You may be given a fraction to substitute. Think about what that would look like.
I would change the fraction to a decimal first. Then use the order of operations.

3. You should be able to evaluate a fraction.
Just get a number for the top and a number for the bottom. Then simplify.
Sometimes the problem maybe be set in the context of a word problem given a
formula. Look at this example. You do not need to understand the formula. Just
put in the given numbers and simplify by the order of operations.

4. Now look at page 122 in the book. It is a puzzle giving formulas and numbers to
substitute for the letters in the formula. Each formula has two different sets of
numbers to substitute. Try each formula. The answers are at the right.
You should get one of these numbers for each problem.
Try number 13. Let e = 2 so that you get w = 0.03 (2)3 This gives w = 0.03 (8) or
w = 0.24

5. Now look at page 123 problem 7. This is a geometry formula you might see on the test.
It is on the formula page as the volume of a cone.
V = 1/3 (3.14) (6)2 (10) Everything is basically multiplied after the exponent
is simplilfied.
V = 1/3 (3.14)(36)(10) You can multiply the three numbers on the right.
Then multiply by 1/3 or change 1/3 to .33.
V = 376.8 or close to it. One the test, choose the answer closest to 376.8.

6. On page 124, just look at the problems beginning with number 10. They are just
practice evaluating.
One page 125, I made up a bunch of expressions leading up to the quadratic formula
which we will be looking at in the next several lessons. A few things may look new.
For example, the plus or minus symbol (±) is just a way to say two things at once.
3 ± 4 means 3 + 4 or 7 and also 3 – 4 or -1 at the same time. You save paper and ink!
I just picked three easy numbers for a b, and c. The answers you should get are on
the next page. Try some of them but don’t worry too much.
We will get lots of practice in the next few lessons.
Thanks for trying this lesson without me actually being in the room. I will
be checking the gmail account for your questions during the 5;30-7:00
time slot on Tuesday night. I will try to answer them in emails.