Lessons Writing Equations

Writing Equations

TEK 6.9A

I can

• Write an equation from a verbal sentence.

• Translate an equation into a verbal sentence

• Determine if an equation is true by substituting values into the equation.

Write this as an expression: $6 dollars less than the cost of an xbox.

Open Ended

Write this as an expression: $6 dollars less than the cost of an xbox.

Real world example

I bought 2 bags of gummy worms for $4.50. Write an equation to represent this situation.

2g = 4.50

Key Ideas

• An expression is a mathematical phrase.

• We can translate a verbal phrase into a mathematical expression.

• Example "a number increased by 4" can be translated into the expression n + 4

Key Ideas

• An equation is a mathematical sentence.

• An equation has an equals sign, and expression does not

• Word problems containing words or phrases that describe equality, such as is, equals, is equal to, and is the same as can be translated into equations.

• "A number increased by 4 is 10" can be written as the equation:

• n + 4 = 10

Open Ended

Write an equation to represent the situation:

A number decreased by 8 is 12

A number decreased by 8 is 12

• is means =

• "A number decreased by 8" tells us that a number we don't know should be subtracted by 8

• x - 8 =

• The words after the word is, tells us what should be on the right side of the equation. So 12 should be on the right side of the equation.

• x - 8 = 12

Write an equation to represent the situation.

The total charge for a microwave repair was $81.21 including tax. The tax was $6.70. Write an equation to determine the cost of the visit.

Multiple Choice

1. Ted bought a dolphin poster for $12.  He now has $5.  Which choice models this situation?

• m - 12 = 5
• m - 5 = 12
• m + 5 = 12
• m + 12 = 5

Multiple Choice

Which choice models this situation?
Robyn had some video games, then bought 4 more.  Now she has a total of 10 games.

• v - 4 = 10
• v + 4 = 10
• 10/4 = v
• 4v = 10

Multiple Choice

5.  After dropping 5ºF, the temperature was 37ºF.  Which choice models this situation?

• d - 37 = 5
• d + 5 = 37
• d - 5 = 37
• d + 37 = 5