Rounding

To round a number to a given place, you look at one digit — the one immediately to the right of that place — and follow a single rule:

• If it's 5 or more, round the target digit up.
• If it's 4 or less, leave the target digit and round down.

Either way, every digit after the target place becomes $0$. That's the whole mechanism. Rounding trades exactness for a cleaner, easier-to-reason-about number — useful for estimating, and essential when a fractional answer makes no sense in the real world.

Place value, one digit decides. Round $3472$ to the nearest hundred. The digit right of the hundreds place is the tens digit, $7$. Since $7 \ge 5$, the hundreds round up:

$3472 \rightarrow 3500$

Round $832$ to the nearest ten instead: the ones digit is $2$, which is less than $5$, so it rounds down to $830$.

Real-world: round to fit the situation. You have $100$ cans and boxes that hold $12$. Dividing, $100 \div 12 = 8$ remainder $4$. Eight boxes leave $4$ cans homeless — so you need a ninth box. Here you must round up, no matter how small the remainder, because a leftover still needs a container.

When a question asks "how many do we need to hold everyone," a leftover always costs you one more. Decide before you peek.