Basic Algebra – Lesson 5 – Expressions from Sentences
by Elaine Ernst Schneider
Objective(s): By the end of this lesson the student will be able to: turn word sentences into algebraic expressions.
Pre Class Assignment: Completion of Basic Algebra – Lesson 4
In the first lesson, you learned that numbers and variables form sentences, or algebraic “expressions.” When you take information from a sentence and turn it into a mathematical expression, it is called “translating.” In another lesson, you learned that when you write algebraic expressions, use +, -, and = signs; and for division, use / , the same way you know that when you see a fraction, it means to divide the top number by the bottom
number. Then, for multiplication, we learned to write the expression with no symbol or sign between them (such as 3a), with an X , or using parentheses. The parenthesis is especially useful in longer problems such as (3y)(4-2x).
Then you learned how to work problems where there are no parentheses or brackets, using the Order of Operations rule. Multiply, Divide, Add, Subtract.
Now let’s put all of this to use and Yes, that’s right! We’re going to take English sentences – WORDS – and turn them into algebraic expressions.
Let’s Get Started:
Subtract seven from twenty-one, then add three.
The algebraic expression is: 21 – 7 + 3
No parentheses are needed because the Order of Operations tells us that addition and subtraction are done in order from left to right.
Now it’s time for you to try a few. Remember your terms: subtract, sum, product, division, multiply, quotient. You may have to use parenthesis on some of them.
Assignment(s) including Answer key:
1. Subtract 2 from x; then add y.
2. Subtract the sum of 2 and y from x.
3. Divide 10 by 3; then multiply by 5.
4. Divide x by the product of 3 and z.
5. Multiply x by 3; then add y.
6. Add x and 3; then multiply by y.
7. Subtract the product of 5 and x from 7.
8. 5 more than the product of 3 and c.
9. 13 less than the quotient 5 divided by p.
10. 4 times the sum of 10 and x.
For Answers, Click Here
Pre-Requisite To: Basic Algebra Lesson 6