HOW TO ADD AND SUBTRACT DECIMALS: 1. First, line up the decimals in a vertical format. 2. Begin on far right column and add or subtract the column. Carry any tens to the next column. (Normal addition or subtraction) 3. Carry any tens OVER the decimal. In other words, ignore the decimal in addition and subtraction and just bring it down to the answer as its own column. 123.456 987.01 + 123. 980 - 123.45 247.436 863.56
HOW TO MULTIPLY DECIMALS: 1. No need to line up decimals. 2. A "factor" is a number being multiplied by another factor or number. 2. Put the factor with less digits on the bottom and the other on top. 3. Multiply as usual. 4. Count the number of decimal places in the top factor and put it in (parenthesis) beside the factor. (see example below) 5. Count the number of decimal places in the bottom factor and put it in parenthesis beside the factor. 6. Add the 2 numbers in parenthesis. This is how many decimal places your answer needs to have.
HOW TO DIVIDE DECIMALS WHEN THE DIVISOR IS A WHOLE NUMBER ____quotient____ divisor = 4 l 15.98 = dividend
1. Take the decimal for the quotient and put it directly above the decimal in the dividend. 2. Divide as you normally would 3.995 4l 15.980 -12 3 9 -36 3 8 -36 20 - 20 0
HOW TO DIVIDE WHEN THE DIVISOR IS A DECIMAL: 1. See above for definition of divisor, dividend and quotient. 2. The divisor MUST be a whole number in order to divide, so when the divisor is a decimal, move the decimal to the right as many places as needed to make it a whole number. 3. Now you must also move the decimal in the dividend that same number of places to the right. 4. Place the decimal in the quotient directly above the new decimal place. (a) quotient (b) (c) . .04 l 15.98 .04 l 15.98 04 l 1598. ^ ^ (d) 399.5 04 l 1598.00 -12 39 -36 38 -36 2 0 - 2 0 0