The ratio of green balls to yellow balls in a bag is . When 9 balls of each colour are removed, the ratio of green balls to yellow balls becomes . How many balls were originally in the bag?
, 2020
Pick one
Solution
Each four-digit number must be greater than 2000, and so the smallest two-digit number that may be repeated is 20 (to give 2020).
Each four-digit number must be less than 10 000, and so the largest two-digit number that may be repeated is 99 (to give 9999).
Each two-digit number between 20 and 99 may be repeated to give a four-digit number between 2000 and 10 000.
In total, there are numbers that satisfy the given conditions.
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