Expressions, Equations and Formulae

What is a variable ?

• A symbol, usually a letter, that can represents different values

• Replace part of an expression, usually a letter, with a another value, usually a number

• The number in front of a variable in algebraic expression or equation

• A number on its own with no variable

Expanding brackets: 4(n-5)

• 4n-5

• 4n-20

• 4n+20

• 4n+5

find x: 4x + 10 = 30

• x=5

• x=6

• x=4

• x=-5

Find n: 6n = 30

• n=10

• n=5

• n=-5

• n=-10

Alex thinks of a number, n.

Write an expression for the number Alex gets when

a) she multiplies the number by 2

b) she adds 5 to the number

Simplify these expressions by collecting like terms.

a) 3c+4c+9d−2d

• 14

• 7c + 7d

• 7cd

• None

Work out the value of p−q

when p=15 and q=3

• 10

• 18

• 12

• 0

Work out the value of the expression:

2a + 3 when a = 8

• 19

• 20

• 13

• 30

• 7

• 4

• 5

• 0

Loli lives with three friends. They share the gas bill equally between the four of them. Write a formula to work out the amount they each pay in letters. (Let t represent the total bill)

• 4t

• t-4

• t+4