Ratio, proportion and rates of changeKS3 / GCSE

Forming from given values

Find the constant and form a direct proportion equation.

  • In direct proportion, is constant.
  • Use , where is a constant.
  • Substitute the known pair, solve for , then write the equation.

Example 1

is directly proportional to . When , . Find an equation connecting and .

Write the proportionality as an equation with constant .Substitute the known pair.Simplify the numerical terms and collect like terms.

Example 2

is directly proportional to . When , . Find an equation connecting and .

Write the proportionality as an equation with constant .Substitute the known pair.Simplify the numerical terms and collect like terms.

Your turn

Question 1

is directly proportional to . When , . Find an equation connecting and .

Check answer
Write the proportionality as an equation with constant .Substitute the known pair.Simplify the numerical terms and collect like terms.
Question 2

is directly proportional to . When , . Find an equation connecting and .

Check answer
Write the proportionality as an equation with constant .Substitute the known pair.Simplify the numerical terms and collect like terms.
Question 3

is directly proportional to . When , . Find an equation connecting and .

Check answer
Write the proportionality as an equation with constant .Substitute the known pair.Simplify the numerical terms and collect like terms.
Question 4

is directly proportional to . When , . Find an equation connecting and .

Check answer
Write the proportionality as an equation with constant .Substitute the known pair.Simplify the numerical terms and collect like terms.
Question 5

is directly proportional to . When , . Find an equation connecting and .

Check answer
Write the proportionality as an equation with constant .Substitute the known pair.Simplify the numerical terms and collect like terms.
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