Understand Number Lines
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The document discusses rounding numbers to the nearest ten. It provides examples of rounding various numbers like 82 to 80, 17 to 20, and 95 to 100. Numbers with 5 in the ones place are rounded up to the next ten. The strategy for rounding to the nearest ten is explained - numbers with 1-4 in the ones place round down, and numbers with 5-9 round up. Practice examples are given to find the range of numbers that would round to 50, 570, and 5000.
Understand Number Lines
- 2. Finding the interval scales. Step 1: To find out how many values each unit represents: (90 -80 =10) Step 2: To find out how many values each sub-unit represents: (10 ÷ 10 = 1 ) Recall… 80 90 1 Sub-unit 1 Unit +1 +1 +1 +1 +1 +1 +1 +1 +1 +1
- 3. What is the value indicated with the letters? Recall… 80 90 1 Sub-unit 1 Unit b b) 80 + 7 = 87 a a) 80 + 5 = 85 +1 +1 +1 +1 +1 +1 +1
- 4. WB page 17 Q1 Use the number line to answer Question (I) Mark each of the following numbers with a cross (X) on the number line above. 48 35 26 20 30 40 50 26 35 48
- 5. Ribbon A is 82 cm long. 82 is between 80 and 90. It is nearer to 80 than to 90. 82 is 80 when rounded off to the nearest ten. 82 is approximately equal to 80. 82 80 80 85 90 82
- 6. Ribbon B is 17 cm long. 10 20 15 17 17 is between 10 and 20. It is nearer to 20 than to 10. 17 is 20 when rounded off to the nearest ten. 17 is approximately equal to 20. 17 20
- 7. Ribbon C is 95 cm long. 90 100 95 95 95 is exactly halfway between 90 and 100. 95 is 100 when rounded off to the nearest ten. 95 100 Why numbers with 5 in the ones place is rounded off to the next tens? The number 5 is at the centre. The convention is to round off the number to the next tens.
- 8. ‘ Rounding off to the nearest ten’ Strategy A number with 1,2,3 or 4 in the ones place is rounded off to the tens before the number. A number with 5,6,7,8 or 9 in the ones place is rounded off to the next tens after the number.
- 9. Find all the numbers that give the following answer when rounded off to the nearest ten. 50 Answer: 45, 46, 47, 48, 49, 50, 51, 52, 53 and 54 Note: The greatest value before it was rounded off is 54. The smallest value before it was rounded off is 45.
- 10. Practice time... (Do Maths TB page 26 Qns 10a and b)
- 11. Find all the numbers that give the following answer when rounded off to the nearest ten. (ii) 570 Answer: 565, 566, 567, 568, 569, 571, 572, 573 and 574 Note: The greatest value before it was rounded off is 574. The smallest value before it was rounded off is 565.
- 12. Find all the numbers that give the following answer when rounded off to the nearest ten. (iii) 5000 Answer: 4995, 4996, 4997, 4998, 4999, 5001, 5002, 5003 and 5004 Note: The greatest value before it was rounded off is 5004. The smallest value before it was rounded off is 4995.