If the base of a rectangle is increased by 10% and the area is
unchanged, by what percentage (exactly) is the width decreased by ?
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
If a sum invested gains 10% each year how long before it has
doubled its value?
But the result numbers are disguised - their digits are replaced by letters.
A given letter stands for the same numeral every time it appears in that column.
For example, whatever the C stands for, it stands for that numeral every time the C appears.
Can you work out the percentage change, even with the result digits in code?
What about this next set?
It's a new coding - the letters now stand for different numerals.
What is the percentage change used on all numbers in the first column this time?
Different coding again, and much harder.
By now the problem has definitely become a three star challenge - fancy having a crack at it?