Rounding Numbers Part 1 © T Madas
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 40 The rounded number must have a zero at the end © T Madas
Rounding to the nearest 10 Round 154 to the nearest 10 150 150 154 160 The rounded number must have a zero at the end © T Madas
Rounding to the nearest 10 Round 125 to the nearest 10 120 125 130 130 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 100 764 700 800 800 The rounded number must have 2 zeros at the end © T Madas
Rounding to the nearest 100 Round 1235 to the nearest 100 1235 1200 1200 1300 The rounded number must have 2 zeros at the end © T Madas
Rounding to the nearest 100 Round 850 to the nearest 100 800 850 900 900 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 0s, 10s, 20s, 30s and 40s get rounded down Numbers ending in 50s, 60s, 70s , 80s and 90s get rounded up Examples: 237 200 1168 1200 874 900 2032 2000 536 500 5750 5800 350 400 40081 40100 © T Madas
Rounding to the nearest 1000 Round 7761 to the nearest 1000 7761 7000 8000 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 8000 8000 9000 The rounded number must have 3 zeros at the end © T Madas
Rounding to the nearest 1000 Round 6500 to the nearest 1000 6000 6500 7000 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 00s, 100s, 200s, 300s and 400s get rounded down Numbers ending in 500s, 600s, 700s , 800s and 900s 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… …10 …100 …1000 48 87 184 145 1563 3217 2005 50 90 180 150 1560 3220 2010 209 2867 3467 1095 1550 45678 61981 200 2900 3500 1100 1600 45700 62000 3456 5349 89231 37849 32489 49838 71974 3000 5000 89000 38000 32000 50000 72000 …whole number 2.7 4.2 10.4 3 4 10 27.9 7.67 33.37 28 8 33 31.436 764.92 0.86 31 765 1 © T Madas
Round these numbers to the nearest… …10 …100 …1000 78 67 181 125 1343 3787 1998 80 70 180 130 1340 3790 2000 279 2557 23107 16915 1850 49805 61041 300 2600 23100 16900 1900 49800 61000 76532 64543 37859 90832 98114 89575 70456 77000 65000 38000 91000 98000 90000 70000 …whole number 2.8 8.2 11.4 3 8 11 37.9 7.17 39.67 38 7 40 37.685 344.02 0.81 38 344 1 © T Madas
Quick Test on Rounding to the nearest… © T Madas
Round these numbers to the nearest… …10 …100 …1000 48 87 184 145 1563 3217 2005 50 90 180 150 1560 3220 2010 209 2867 3467 1095 1550 45678 61981 200 2900 3500 1100 1600 45700 62000 3456 5349 89231 37849 32489 49838 71974 3000 5000 89000 38000 32000 50000 72000 …whole number 2.7 4.2 10.4 3 4 10 27.9 7.67 33.37 28 8 33 31.436 764.92 0.86 31 765 1 © T Madas
Round these numbers to the nearest… …10 …100 …1000 78 67 181 125 1343 3787 1998 80 70 180 130 1340 3790 2000 279 2557 23107 16915 1850 49805 61041 300 2600 23100 16900 1900 49800 61000 76532 64543 37859 90832 98114 89575 70456 77000 65000 38000 91000 98000 90000 70000 …whole number 2.8 8.2 11.4 3 8 11 37.9 7.17 39.67 38 7 40 37.685 344.02 0.81 38 344 1 © T Madas
Rounding Numbers Part 2 © T Madas
Rounding decimals… to the nearest whole number We look at the 1st 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 2nd decimal place If it is 0, 1, 2, 3 or 4 we just throw the 2nd, the 3rd, the 4th … decimal digits away If it is 5, 6, 7, 8 or 9 we throw the 2nd, the 3rd, the 4th … decimal digits away and we increase the 1st 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 3rd decimal place If it is 0, 1, 2, 3 or 4 we just throw the 3rd, the 4th, the 5th … decimal digits away If it is 5, 6, 7, 8 or 9 we throw, the 3rd, the 4th, the 5th … decimal digits away and we increase the 2nd 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 1 decimal places 3 2 3.117 2.724 9.2341 1.867 1.9 1.3173 1.32 2.226 2.2258 5.5 5.471 9.49 9.48973 1.48173 1.482 0.43456 4.1424 0.10704 6.39745 6.4 2.36 2.3553 5.36581 5.366 5.245567 0.46878 0.47 6.40078 6.401 1.6 1.56437 2.59 2.585423 4.090 4.089623 4.6751 4.7 3.5024 3.5004 0.9034 7.31 7.3058 8.533 8.5328 8.8 8.75438 0.49878 0.50 0.49978 0.500 © T Madas
Quick Test on Number Rounding to Decimal Places © T Madas
1 d.p. 2 d.p. 3 d.p. Round the following numbers to decimal places 3.117 2.724 9.2341 1.9 1.867 1.32 1.3173 2.2258 2.226 5.5 5.471 9.49 9.48973 1.48173 1.482 0.43456 4.1424 0.10704 6.4 6.39745 2.36 2.3553 5.36581 5.366 © T Madas
1 d.p. 2 d.p. 3 d.p. Round the following numbers to decimal places 5.245567 0.47 0.46878 6.40078 6.401 1.6 1.56437 2.59 2.585423 4.089623 4.090 4.7 4.6751 3.5024 3.5004 0.9034 7.31 7.3058 8.533 8.5328 8.75438 8.8 0.49878 0.50 0.500 0.49978 © T Madas
© T Madas