Round It Up! Rounding to 10 and 100

Imagine you scored 47 points in a game. Your friend says, 'That's almost 50!' Are they right? How do they know? Numbers do not always land on a neat 10 or 100, so we round them — we find the nearest tidy number. This makes estimating and comparing much easier. Think about this: is 47 closer to 40 or closer to 50? How can you tell?

Rounding means replacing a number with a nearby number that is easier to work with. We round to the nearest 10 or the nearest 100. **Rounding to the nearest 10** Look at the ones digit (the last digit on the right). This tells you which way to round. • If the ones digit is 0, 1, 2, 3, or 4 — round DOWN. Keep the tens digit the same and change the ones to 0. • If the ones digit is 5, 6, 7, 8, or 9 — round UP. Add 1 to the tens digit and change the ones to 0. Example: Round 63 to the nearest 10. The ones digit is 3 — that is less than 5, so round down. Answer: 60. Example: Round 78 to the nearest 10. The ones digit is 8 — that is 5 or more, so round up. Answer: 80. **Rounding to the nearest 100** Now look at the tens digit (the middle digit in a three-digit number). Use the same rule. • Tens digit 0–4 → round DOWN to the lower hundred. • Tens digit 5–9 → round UP to the higher hundred. Example: Round 340 to the nearest 100. The tens digit is 4 — less than 5, so round down. Answer: 300. Example: Round 570 to the nearest 100. The tens digit is 7 — that is 5 or more, so round up. Answer: 600. **The halfway rule** is the key idea: 5 is the halfway point, and we always round UP when we reach it.