There are **16** NRICH Mathematical resources connected to **Calculating with percentages**, you may find related items under Fractions, Decimals, Percentages, Ratio and Proportion.

Your school has been left a million pounds in the will of an ex- pupil. What model of investment and spending would you use in order to ensure the best return on the money?

If a sum invested gains 10% each year how long before it has doubled its value?

There are two sets of numbers. The second is the result of the first after an increase by a constant percentage. How can you find that percentage if one set of numbers is in code?

Would you rather: Have 10% of £5 or 75% of 80p? Be given 60% of 2 pizzas or 26% of 5 pizzas?

All CD Heaven stores were given the same number of a popular CD to sell for £24. In their two week sale each store reduces the price of the CD by 25% ... How many CDs did the store sell at. . . .

A political commentator summed up an election result. Given that there were just four candidates and that the figures quoted were exact find the number of votes polled for each candidate.

Can you match the cards and figure out whether the tabloid headlines can be trusted?

When Charlie retires, he's looking forward to the quiet life, whereas Alison wants a busy and exciting retirement. Can you advise them on where they should go?

Go through the maze, collecting and losing your money as you go. Which route gives you the highest return? And the lowest?

Charlie thinks that a six comes up less often than the other numbers on the dice. Have a look at the results of the test his class did to see if he was right.

For teachers. Yet more school maths from long ago-interest and percentages.

Tim and Beth both have a string of flags. Use the percentages to find out who has the most flags.

Find the exact difference between the largest ball and the smallest ball on the Hepta Tree and then use this to work out the MAGIC NUMBER!

If the base of a rectangle is increased by 10% and the area is unchanged, by what percentage is the width decreased by ?

In my local town there are three supermarkets which each has a special deal on some products. If you bought all your shopping in one shop, where would be the cheapest?