CONSTRUCTING EQUATIONS

Example

A table top measures x cm by y cm. Write down an expression for its area, A.

Example

The sides of a rectangle are A cm and B cm. Write down an

expression for the perimeter of the rectangle.

Example

A packet of chewing gum holds 8 sticks of gum.

How many sticks are there in

(i) 3 packets

(ii) 8 packets

(iii) x packets?

Example

A classroom in the new building is designed to hold 35 pupils.

How many pupils can be seated in

(i) 2 rooms

(ii) 5 rooms

(iii) R rooms?

Example

The number B is the sum of two numbers x and y.

write down an expression for B.

Example

The cost of a pen is 9 pence.

What is the cost of

(i) 3 pens

(ii) 12 pens

(iii) n pens?

Example

Alan is three years younger than his sister Fiona. If Fiona is y

years old write down an expression for Alan’s Age.

If Fiona’s mum is three times her age. Write down an expression

for her age.

Example

The sum of three numbers is S and two of the numbers are a

and b. What is the third number ?

Example

A pen and pencil together costs x pence, and a pen alone

costs y pence. Find the cost of three pencils.

Example

The cost of a school outing to the theatre is £ C for the hire of

the coach plus £5 per child for tickets

a) Write down an expression for the cost of 20 children

b) When n children attend the theatre the total cost is £ T

Write a formula for T in terms of C and n.

Example

A bag of sweets is handed around the class and each student takes

4 sweets from the bag.

a) If there are C people in the class, how many sweets are taken from

the bag?

b) If there are 5 sweets left in the bag, and there were S sweets in the

bag at the start, write down a formula connecting S and C.