Round to the nearest 10, 100 and 1000

What you will learn

• Round to the nearest 10, 100 and 1000

Models used: number sentences, stories, diagrams.

Before you start

• Represent and compare numbers to 100000

Which ten is closer?

46 sits between 40 and 50. Which end is closer?

1. Start at the marked number. A jump to the right adds; a jump to the left takes away. Read the size of each jump.

   46 sits between 40 and 50. Which end is closer?

2. Start at the marked number. A jump to the right adds; a jump to the left takes away. Read the size of each jump.

   45 is halfway. 46 has already passed the halfway point towards 50.

3. Start at the marked number. A jump to the right adds; a jump to the left takes away. Read the size of each jump.

   It takes 4 steps to reach 50, but 6 to reach 40. So 46 rounds to 50.

   46 ≈ 50

4. The complete bar is the whole. Each labelled section is one part of it.

   An estimate checks the size of an answer: 46 + 32 is about 50 + 30, or 80.

   46 + 32 = 78, close to 80

   80

   5030

Worked example: A new example, together

Round 10739 to the nearest 1000.

1. Locate both endpoints, then the halfway point and the number itself.

   Rounding chooses a nearby benchmark, so the result is approximate.

   100001073911000

2. Neighbouring multiples: 10000 and 11000.

   100001073911000

   Round 10739 to the nearest 1000.

   11000

3. The halfway point is 10500.

   100001073911000

4. Choose the nearer multiple; a halfway value rounds up: 11000.

   100001073911000

5. Check the result against the question we started with.

   10739 ≈ 11000; the distance is no more than 500.

   We found 11000. Rounding chooses a nearby benchmark, so the result is approximate.

   100001073911000

Common mistakes to discuss

• Reading every following digit. Only the digit in the next smaller place decides. Rounding 2449 to the nearest hundred looks at the 4 tens, so it gives 2400, not 2500.

Check your understanding

• Round to the nearest 10, 100 and 1000
• use neighbouring benchmarks and the midpoint to justify an estimate
• check the answer against the original quantities and units

Explain your reasoning to an adult, then try a fresh question in the interactive lesson. A result from one attempt is not proof of lasting mastery.