Fractions and decimals both represent numbers that are not whole numbers. Fractions describe a part of a whole. The number on the bottom of the fraction, called the denominator, indicates how many parts the whole is divided into. The top number of the fraction, called the numerator, tells how many parts you have. When you convert a fraction into a decimal number, it is the same as converting the fraction into an equivalent fraction with a denominator that is a power of 10. Converting fractions to decimals can make other calculations easier.
Write a fraction on the board (for example, 5/25) and tell the students to look at the fraction you want to convert to a decimal number. Tell them the line separating the numerator (upper number of the fraction) and denominator (bottom number of the fraction) is called the fraction bar, or division bar.
Instruct the students that there is more than one way to name (or read) a fraction. The fraction can be read as five twenty-fifths, or as the numerator divided by the denominator, 5 divided by 25. 5/25 is the same as 5 ÷ 25.
Tell the students you are going to divide the numerator of the fraction, 5, by the denominator, 25. Set up the problem on the board, and show each step of the problem as you discuss it.
Ask the students to tell you the first step in the division problem. Place a decimal point after the “5” and add a “0”. Write another decimal point above the division symbol, directly over the first decimal point.
Write a “0” in front of the decimal point because 25 can’t divide into 5. Ask the students how many times 25 divides into 50. Write the answer, 2, behind the decimal point.
Tell the students that 5/25, converted into a decimal, is 0.2. Continue to practice using increasingly more difficult fractions, until the students understand the concept.