Rational Numbers & Equations Lesson 21 Rational Numbers & Equations Dividing Rational Numbers

Warm-Up Find the value of each expression. 0.14 ÷ 0.2 325 ÷ 2.5

Dividing Rational Numbers Target: Find quotients of positive and negative fractions and decimals.

Dividing Positive and Negative Rational Numbers Determine the sign of the quotient. The quotient of two numbers with the same sign is positive. The quotient of two numbers with different signs is negative. Find the quotient as if working with positive numbers. Then put the sign on the quotient.

Example 1 9.36 ÷ (–5.2) The numbers have different signs, so the quotient will be negative. Move the decimal point in the divisor. 5.2 → 52 Move the decimal in the dividend the same number of spaces as in the divisor. 9.36 → 93.6 Divide. 9.36 ÷ (–5.2) = –1.8

Example 2 The numbers have the same signs, so the answer will be positive. Write as improper fractions. Multiply by the reciprocal. Simplify.

Example 3 Scott bought a bag of cake flour that contained cups of flour. He makes muffins to sell at his bakery. Each batch of muffins requires cups of flour. Determine how many batches of muffins he can make with this bag of flour. Write the problem. Same signs. The answer will be positive. Write as improper fractions. Multiply by the reciprocal. Scott will be able to make 11 batches.

Exit Problems Find each quotient. 120.8 ÷ (–0.4)

Communication Prompt What clues do you look for when reading word problems to figure out which operation (+, –, ×, ÷) you will use?