There is someone who wants to spread a rumor within 7 days to 250,000,000 people. he wants to know how many people he should tell on the first day (assuming the rumor is passed by everyone who was told to the same amount of people) so that everyone knows on the 7th day.
What I did is the 7th root of 250,000,000. this answer is not possible unless rounded. is it okay for the number to be approximate?
I would do exactly what you did. Take the seventh root of 250 000 000. You have to be careful to round up regardless of how small the decimal part. If you round down then the seventh power will be less than 250 000 000.