Writing Expressions

Expressions vs. Equations Expressions use numbers, number symbols and letters (variables) to explain a sentence. Equations are like expressions except they have an equal sign.

examples twelve divided by three Twenty increased by eleven 12 ÷ 3 Twenty increased by eleven 20 + 11 Thirty-seven minus a number 37 - n

Real life problem Joey mows lawns to make some extra money. He charges $21 for each lawn and an extra $2 per hour. Which expression should he use to find out how much to charge his customers? [A] 21 + h [B] 21 + 2·h [C] 21 + 2 [D] 21 – 2·h

Translating words into symbols Addition Subtraction Multiplication Division Sum Difference Product Quotient Increase Decrease Factors Equally shared More than Less than Times Divided by Plus Minus Multiplied by Added to of

Example problems Twelve pieces of candy equally shared by four friends 12 ÷ 4 The product of seven and four 7 x 4 The difference of Twenty and sixteen 20 – 16 y less than 18 times 6 18 • 6 – y

Example problems Seven decreased by five The product of four and nine 7 – 5 The product of four and nine 4 x 9 The sum of a number and ten m + 10 Eight more than a number c c + 8

Example problems The quotient of twenty and two Five minus a number x 20 ÷ 2 Five minus a number x 5 – x Five less than a number x x – 5 Eighteen equally shared by six 18 ÷ 6

Example problems Three times the sum of a number and 5 3 x (n + 5) The quotient of m and 2 plus 7. (m ÷ 2) + 7 four times the quantity of x minus 8 4 x (x – 8) Eight more than the product of a number and 9 c + 8