T Madas Sometimes we have to round numbers

Sometimes we have to round numbers What does rounding mean? Can you think of some examples? © T Madas

Rounding to the nearest 10 Round 37 to the nearest 10 30 37 40 The rounded number must have a zero at the end © T Madas

Rounding to the nearest 10 Round 154 to the nearest 10 154 160 The rounded number must have a zero at the end © T Madas

Rounding to the nearest 10 Round 125 to the nearest 10 125 130 When our number lies halfway between “tens”, we have agreed to round the number up. © T Madas

Rounding to the nearest 10 Numbers ending in 1, 2, 3 and 4 get rounded down Numbers ending in 5, 6, 7 , 8 and 9 get rounded up Examples: 27 30 68 70 94 90 132 130 146 150 565 570 305 310 481 480 © T Madas

Rounding to the nearest 100 Round 764 to the nearest 100 764 800 The rounded number must have 2 zeros at the end © T Madas

Rounding to the nearest 100 Round 1235 to the nearest 100 1235 1300 The rounded number must have 2 zeros at the end © T Madas

Rounding to the nearest 100 Round 850 to the nearest 100 850 900 When our number lies halfway between “hundreds”, we have agreed to round the number up. © T Madas

Rounding to the nearest 100 Numbers ending in 0 s, 10 s, 20 s, 30 s and 40 s get rounded down Numbers ending in 50 s, 60 s, 70 s , 80 s and 90 s get rounded up Examples: 237 200 1168 1200 874 900 2032 2000 536 500 5750 5800 350 40081 40100 © T Madas

Rounding to the nearest 1000 Round 7761 to the nearest 1000 7761 8000 The rounded number must have 3 zeros at the end © T Madas

Rounding to the nearest 1000 Round 8339 to the nearest 1000 8339 9000 The rounded number must have 3 zeros at the end © T Madas

Rounding to the nearest 1000 Round 6500 to the nearest 1000 6500 7000 When our number lies halfway between “thousands”, we have agreed to round the number up. © T Madas

Rounding to the nearest 1000 Numbers ending in 00 s, 100 s, 200 s, 300 s and 400 s get rounded down Numbers ending in 500 s, 600 s, 700 s , 800 s and 900 s get rounded up Examples: 2837 3000 1868 2000 4874 5000 2499 2000 5376 5000 29780 30000 7500 8000 45681 46000 © T Madas

Practice Rounding to the nearest… © T Madas

Round these numbers to the nearest… … 1000 48 50 209 200 3456 3000 87 90 2867 2900 5349 5000 184 180 3467 3500 89231 89000 145 150 1095 1100 37849 38000 1563 1560 1550 1600 32489 32000 3217 3220 45678 45700 49838 50000 2005 2010 61981 62000 71974 72000 …whole number 2. 7 3 27. 9 28 31. 436 31 4. 2 4 7. 67 8 764. 92 765 10. 4 10 33. 37 33 0. 86 1 © T Madas

Round these numbers to the nearest… … 1000 78 80 279 300 76532 77000 67 70 2557 2600 64543 65000 181 180 23107 23100 37859 38000 125 130 16915 16900 90832 91000 1343 1340 1850 1900 98114 98000 3787 3790 49805 49800 89575 90000 1998 2000 61041 61000 70456 70000 …whole number 2. 8 3 37. 9 38 37. 685 38 8. 2 8 7. 17 7 344. 02 344 11 39. 67 40 0. 81 1 © T Madas

Quick Test on Rounding to the nearest… © T Madas

Round these numbers to the nearest… … 1000 48 50 209 200 3456 3000 87 90 2867 2900 5349 5000 184 180 3467 3500 89231 89000 145 150 1095 1100 37849 38000 1563 1560 1550 1600 32489 32000 3217 3220 45678 45700 49838 50000 2005 2010 61981 62000 71974 72000 …whole number 2. 7 3 27. 9 28 31. 436 31 4. 2 4 7. 67 8 764. 92 765 10. 4 10 33. 37 33 0. 86 1 © T Madas

Round these numbers to the nearest… … 1000 78 80 279 300 76532 77000 67 70 2557 2600 64543 65000 181 180 23107 23100 37859 38000 125 130 16915 16900 90832 91000 1343 1340 1850 1900 98114 98000 3787 3790 49805 49800 89575 90000 1998 2000 61041 61000 70456 70000 …whole number 2. 8 3 37. 9 38 37. 685 38 8. 2 8 7. 17 7 344. 02 344 11 39. 67 40 0. 81 1 © T Madas

Rounding decimals… to the nearest whole number We look at the 1 st decimal place • If it is 0, 1, 2, 3 or 4 we just throw all the decimal digits away • If it is 5, 6, 7, 8 or 9 we throw all the decimal digits away and we increase the units by 1 Examples: 23. 7 24 1. 768 2 8. 94 9 20. 32 20 53. 6 54 5. 8757 6 3. 52 4 40. 071 40 © T Madas

Rounding decimals… to one decimal place We look at the 2 nd decimal place • If it is 0, 1, 2, 3 or 4 we just throw the 2 nd, the 3 rd, the 4 th … decimal digits away • If it is 5, 6, 7, 8 or 9 we throw the 2 nd, the 3 rd, the 4 th … decimal digits away and we increase the 1 st decimal digit by 1 Examples: 3. 734 3. 7 5. 728 5. 7 8. 294 8. 3 41. 32 41. 3 9. 16 9. 2 5. 8757 5. 9 6. 52 6. 5 40. 071 40. 1 © T Madas

Rounding decimals… to two decimal places We look at the 3 rd decimal place • If it is 0, 1, 2, 3 or 4 we just throw the 3 rd, the 4 th, the 5 th … decimal digits away • If it is 5, 6, 7, 8 or 9 we throw, the 3 rd, the 4 th, the 5 th … decimal digits away and we increase the 2 nd decimal digit by 1 Examples: 3. 7342 3. 73 5. 7028 5. 70 5. 2863 5. 29 4. 3592 4. 36 0. 1605 0. 16 5. 8957 5. 90 2. 5782 2. 58 4. 9971 5. 00 © T Madas

Practice Rounding to Decimal Places © T Madas

Round the following numbers to 3 1 2 decimal places 3. 117 2. 724 9. 2341 1. 9 1. 867 1. 32 1. 3173 2. 226 2. 2258 5. 471 5. 5 9. 49 9. 48973 1. 482 1. 48173 0. 43456 4. 1424 0. 10704 6. 39745 2. 36 2. 3553 5. 366 5. 36581 5. 245567 0. 46878 6. 401 6. 40078 1. 6 1. 56437 2. 59 2. 585423 4. 090 4. 089623 4. 7 4. 6751 3. 5024 3. 5004 0. 9034 7. 31 7. 3058 8. 533 8. 5328 8. 75438 0. 50 0. 49878 0. 500 0. 49978 © T Madas

Quick Test on Number Rounding to Decimal Places © T Madas

Round the following numbers to decimal places 1 d. p. 2 d. p. 3. 117 2. 724 9. 2341 1. 9 1. 867 1. 32 1. 3173 2. 226 2. 2258 5. 471 5. 5 9. 49 9. 48973 1. 482 1. 48173 0. 43456 4. 1424 0. 10704 6. 39745 2. 36 2. 3553 5. 366 5. 36581 © T Madas

Round the following numbers to decimal places 1 d. p. 2 d. p. 3 d. p. 5. 245567 0. 46878 6. 401 6. 40078 1. 6 1. 56437 2. 59 2. 585423 4. 090 4. 089623 4. 7 4. 6751 3. 5024 3. 5004 0. 9034 7. 31 7. 3058 8. 533 8. 5328 8. 75438 0. 50 0. 49878 0. 500 0. 49978 © T Madas