DECIMALS ADDING or SUBTRACTING DECIMALS Place Value Chart 3 4 5 6 7 1 2 3 4 Example: Ten-Thousandths Thousandths Hundredths Ones Tens Hundreds Thousands Ten Thousands Hundred thousands Millions . Tenths 2 (and) 1 To add or subtract decimals, Line up the decimals – bring decimal straight down. Add decimal at the end of whole numbers to fill gaps Example: 54.03 3.20 57.23 Example: 30 - 1.64 = 6.000 .345 + 14.010 20.355 29 910 30.00 1.64 28.36 WRITING DECIMALS To write a decimal in standard form, Look at the word after the number. This word tells you where to put the last digit in the number. Using the place value chart, write the numbers in the correct position in the chart. Add zeros as placeholders to fill space between any number and the decimal. Example: 75 thousandths MULTIPLYING DECIMALS to multiply decimals, DO NOT LINE THE DECIMAL POINTS UP , count how many numbers are behind the decimals in the problem. Place the decimal the same number of spaces to the left in the answer. Add zeros if necessary. Example: . 0 7 Example: . 045 5 Ten-Thousandths Thousandths Hundredths Tenths (and) Ones Tens Hundreds Thousands Ten Thousands Hundred Thousands Millions DIVIDING DECIMALS To divide a decimal by a whole number, move the decimal straight up and divide as usual Example: To write a decimal in words, write the whole number in words. Write the word and for the decimal point. Write the decimal part in words. Then write the place name of the last digit. Example: = One and three hundred eight thousandths = thirty-five hundredths ROUNDING DECIMALS To round decimals, locate the place value of the number being rounded, look at the digit to the right of that place value. If the number is 5 or more, add 1 to the place value number. If it is less than 5, the number stays the same. (move 3 spaces, add zero) (move 3 spaces ) 3.02 2 6.04 To divide a decimal by another decimal, move the decimal on the outside to the end of the number. Then move the decimal the same number of spaces on the inside Example: . 06 5.412 = 90.2 6 541.2 move 2 places To divide a whole number by a decimal, place a decimal at the end of the whole number first. Then move the decimal the same number of times as you did on the outside. Add zeros to fill in the gaps. Example: 0.2916 rounded to the nearest tenths place = 0.3 Example: 0.0916 rounded to the nearest hundredths place = 0.09 COMPARING DECIMALS To compare decimals, line the decimals up. Starting from the left, compare each number in each column. Any space that is blank in a column, add a zero in its place. less than Example: 0.0027 0.0080 greater than 8 is bigger than 2 therefore: 0 .0027 = equal 0.008 .4 28. .4 28.0 place decimal at end of 28 7 0. 4 280. move 1 space, add a zero To change a decimal to a percent, move the decimal 2 places to the right, add the percent sign. Example: 0.75 = 75% Example: .6 = 60%
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