Problem 3 · From 99% down to 98%
Percentages deceive: the left-hander must go from 1% to 2%.
Integer answer, at most 4 digitsThere are 100 people in a room. 99% are right-handed. How many right-handed people must leave the room so that the percentage of right-handed people remaining is 98%?
Copa Cangur · SCM
Medium
Closed answer
Reasoned solution
Key idea: the trick is to watch the single left-handed person: they don't leave, so they must go from being $1\%$ to being $2\%$ of the room.
If the left-hander is $2\%$ of the total, $50$ people must remain: the left-hander and $49$ right-handers.
$$99 - 49 = 50\ \text{right-handers must leave}.$$
Check: $49/50 = 98\%$ ✓.
Answer: 50