Coaching Centre
Increasing and decreasing by a percentage
Increasing and decreasing amounts by a percentage using multipliers, with discounts, GST and mark-ups.
The multiplier method
The dashed line is no change. Positive r is an increase, negative r is a decrease.
A $\$85$ shirt is discounted by $30\%$. Find the sale price.
A shop buys a bike for $\$240$ and marks it up by $45\%$. Find the selling price.
An $\$85$ shirt is $30\%$ off. Find the sale price.
$85 \times 0.7$.
A $\$240$ bike is marked up by $45\%$. Find the selling price.
$240 \times 1.45$.
$\$100$ is increased by $20\%$ then decreased by $20\%$. Find the result.
$100 \times 1.2 \times 0.8$.
What is the multiplier for a $15\%$ decrease?
$1 - 0.15$.
Add $10\%$ GST to $\$120$.
$120 \times 1.1$.
What is the multiplier for a $7\%$ increase?
$1 + 0.07$.
A $\$50\,000$ car loses $10\%$ of its value. Find the new value.
$50\,000 \times 0.9$.
A population of $560$ grows by $20\%$. Find the new population.
$560 \times 1.2$.
New numbers every time. Keep going until you get five in a row.