A tap drips about 3 times a minute. Roughly how many drips is that in one day?
Hints
Take them one at a time. The first gives nothing away.
1A nudge
Go minute, then hour, then day.
2The strategy
Build the answer one unit at a time rather than in one leap: drips per minute, then per hour, then per day. Check after each step whether the number should have grown.
3The full solution
3 a minute is 3 x 60 = 180 an hour, and 180 x 24 = 4320 a day.
Solution
The reliable way
Take it one unit at a time. Three drips a minute is 3 x 60 = 180 an hour. Over 24 hours that is 180 x 24 = 4320. The transferable idea: convert one step at a time and sanity-check the size after each step, rather than multiplying everything at once and hoping.
The elegant way
A day is about 1440 minutes, and three times that is a little over 4000 — enough to pick the right choice without finishing the arithmetic.
Why this is on the test: Order-of-magnitude questions are answered by picking the nearest choice, and a single missed conversion moves the answer by a factor of sixty.