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

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CD Heaven

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 each price?

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

A Change in Code

Stage: 4 Challenge Level: Challenge Level:1
Notice that whole numbers have stayed as whole numbers after the increase.

What could all the original numbers be divided by without producing a decimal anywhere in the results column?


The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice. More information on many of our other activities can be found here.
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