Writing Expressions from Statements

We can use the rules of simplifying to write down an expression from a statement.

Examples

John has m sweets and Vusi has y sweets. How many sweets do they have altogether?

They have m + y sweets.

These are unlike terms, so we cannot simplify this answer. It is written as an expression.

Lee has 5 more sweets than Parvati. How many sweets does Lee have?

Lee has m + 5 sweets (unlike terms).

Bill has twice as many sweets as Charlize. How many sweets does Bill have?

Bill has 2 x y = 2y sweets (can be simplified to 2y by leaving out the multiply sign).

Janet has half the number of sweets that Thandi has. How many does Janet have?

Jill has 4 less sweets than John.

Jill has m – 4 sweets (unlike terms).

Back to top

Making Equations

More information can be given in order to make an equation.

Example 1:  I multiply a number by 3 and then add 5. If the answer is 32, what was the number?

Let the number be y.

Three times the number = 3y

Add 5 = 3y + 5

Example 2: The length of a rectangle is (m + 3) cm and the width is 5 cm. If the area is 50 cm², find the length of the rectangle.

Area = Length x Width
   50 = ( m + 3) x 5

We need the brackets to show that the 3 and the m together make the length.

The equation is 5(m + 3) = 50.

We can solve this equation to find m.

Example 3: The length of a rectangle is t cm. The width is 5 cm less than the length. If the perimeter is 50 cm, make an equation in t and solve to find the length and width of the rectangle.

Length = a
Width = a – 5
Perimeter = a + a + (a – 5) + (a – 5)

Back to top
Print this page