 # Using Simple Formulae (2)

In this worksheet, students use simple formulae to answer questions. Symbols are used. Key stage:  KS 2

Curriculum topic:  Algebra

Curriculum subtopic:  Use Algebra Formulae

Difficulty level:   ### QUESTION 1 of 10

A formula tells you how to work something out based on what you know already.

If you know the length of the side of a square, how would you work out its perimeter?

The answer is to multiply it by 4, because a square has 4 sides of equal length.

We can use a formula to state this, but first we must say what the letters stand for.

s = side length of square

P = perimeter of square

The formula will be

P = 4s

which means P = 4 × s.

If s = 5,

P = 4 × 5 = 20.

If s = 15,

P = 4 × 15 = 60.

Example

Mum uses the following formula to work out our pocket money.

P = A × 30 ÷ 2 + 100

where P stands for pocket money in pence and A stands for our age in years.

Bill is 5 years old. How much does he get?

Amy is 15 years old. How much does she get?

Bill

A = 5

P = 5 × 30 ÷ 2 + 100 = 150 ÷ 2 + 100 = 75 + 100 = 175 pence

Amy

A = 15

P = 15 × 30 ÷ 2 + 100 = 450 ÷ 2 + 100 = 225 + 100 = 325 pence

The formula for the area of a square is

A = s × s

where:

A = area

s = side length of square.

Use the formula to work out the area when the side length = 8.

The formula for the area of a square is

A = s × s

where:

A = area

s = side length of square.

Use the formula to work out the area when the side length = 12.

The formula for the area of a rectangle is

A = l × w

where:

l = length

w = width.

Use the formula to work out the area when the length is 8 and the width is 5.

The formula for the perimeter P of a rectangle is

P = l × 2 + w × 2

where:

l = length

w = width.

Use the formula to work out the perimeter when the length is 8 and the width is 5.

The formula for the perimeter P of a rectangle is

P = l × 2 + w × 2

where:

l = length

w = width.

Use the formula to work out the perimeter when the length is 12 and the width is 11.

Chef uses this formula to work out the cooking time for a turkey:

T = W × 15 + 60

where T is the time in minutes and W is the weight of the turkey in pounds.

For how many minutes should he cook a 12-pound turkey?

(Just write the number.)

Chef uses this formula to work out the cooking time for a turkey:

T = W × 15 + 60

where T is the time in minutes and W is the weight of the turkey in pounds.

For how many minutes should he cook an 11-pound turkey?

(Just write the number.)

To convert a temperature in Centigrade to one in Fahrenheit, we use this formula:

F = C × 9 ÷ 5 + 32

where

C is the temperature in degrees Centigrade or Celsius

F is the temperature in degrees Fahrenheit.

Use the formula to convert 10 degrees Centigrade to Fahrenheit.

To convert a temperature in Centigrade to one in Fahrenheit, we use this formula:

F = C × 9 ÷ 5 + 32

where

C is the temperature in degrees Centigrade or Celsius

F is the temperature in degrees Fahrenheit.

Use the formula to convert 0 degrees Centigrade to Fahrenheit.

To convert a temperature in Centigrade to one in Fahrenheit, we use this formula:

F = C × 9 ÷ 5 + 32

where

C is the temperature in degrees Centigrade or Celsius

F is the temperature in degrees Fahrenheit.

Use the formula to convert 40 degrees Centigrade to Fahrenheit.

• Question 1

The formula for the area of a square is

A = s × s

where:

A = area

s = side length of square.

Use the formula to work out the area when the side length = 8.

64
EDDIE SAYS
A = 8 × 8 = 64
• Question 2

The formula for the area of a square is

A = s × s

where:

A = area

s = side length of square.

Use the formula to work out the area when the side length = 12.

144
EDDIE SAYS
A = 12 × 12 = 144
• Question 3

The formula for the area of a rectangle is

A = l × w

where:

l = length

w = width.

Use the formula to work out the area when the length is 8 and the width is 5.

40
EDDIE SAYS
A = 8 × 5 = 40
• Question 4

The formula for the perimeter P of a rectangle is

P = l × 2 + w × 2

where:

l = length

w = width.

Use the formula to work out the perimeter when the length is 8 and the width is 5.

26
EDDIE SAYS
P = 8 × 2 + 5 × 2 = 16 + 10 = 26
• Question 5

The formula for the perimeter P of a rectangle is

P = l × 2 + w × 2

where:

l = length

w = width.

Use the formula to work out the perimeter when the length is 12 and the width is 11.

46
EDDIE SAYS
P = 12 × 2 + 11 × 2 = 24 + 22 = 46
• Question 6

Chef uses this formula to work out the cooking time for a turkey:

T = W × 15 + 60

where T is the time in minutes and W is the weight of the turkey in pounds.

For how many minutes should he cook a 12-pound turkey?

(Just write the number.)

240
EDDIE SAYS
W = 12
T = 12 × 15 + 60 = 180 + 60 = 240 minutes
• Question 7

Chef uses this formula to work out the cooking time for a turkey:

T = W × 15 + 60

where T is the time in minutes and W is the weight of the turkey in pounds.

For how many minutes should he cook an 11-pound turkey?

(Just write the number.)

225
EDDIE SAYS
W = 11
T = 11 × 15 + 60 = 165 + 60 = 225 minutes
• Question 8

To convert a temperature in Centigrade to one in Fahrenheit, we use this formula:

F = C × 9 ÷ 5 + 32

where

C is the temperature in degrees Centigrade or Celsius

F is the temperature in degrees Fahrenheit.

Use the formula to convert 10 degrees Centigrade to Fahrenheit.

50
EDDIE SAYS
C = 10
F = 10 × 9 ÷ 5 + 32 = 90 ÷ 5 + 32 = 18 + 32 = 50
• Question 9

To convert a temperature in Centigrade to one in Fahrenheit, we use this formula:

F = C × 9 ÷ 5 + 32

where

C is the temperature in degrees Centigrade or Celsius

F is the temperature in degrees Fahrenheit.

Use the formula to convert 0 degrees Centigrade to Fahrenheit.

32
EDDIE SAYS
C = 0
F = 0 × 9 ÷ 5 + 32 = 0 ÷ 5 + 32 = 0 + 32 = 32
This is the freezing temperature of water.
• Question 10

To convert a temperature in Centigrade to one in Fahrenheit, we use this formula:

F = C × 9 ÷ 5 + 32

where

C is the temperature in degrees Centigrade or Celsius

F is the temperature in degrees Fahrenheit.

Use the formula to convert 40 degrees Centigrade to Fahrenheit.