2.7 solving proportions

Objective: 1. Solve problems using proportions

Ratio: A comparison of two numbers, usually written as a fraction.

Proportion: --An equation stating that two ratios are equal

--(or two equal fractions)

Where b ≠ 0 and d ≠ 0.

What do you notice happens when you multiply the diagonals on the following proportion?

Please solve for x in each of the following.

3 = x

5 20

12 = x

4 = 10

7 x

17.5 = x

7 = 49

X 56

8 = x

3 (20) = 5(x) 7(56) = 49(x) 7(10) = 4(x)

solve for x

4 (x – 8) = 5(x + 3)

4x – 32 = 5x + 15- 5x - 5x______-1x – 32 = 15 + 32 +32

-1x = 47-1x = 47-1 -1 x = - 47

Using a proportion to solve a problem.

A portable media player has 2 gigabytes of storage and can hold about 500 songs. A similar but larger media player has 80 gigabytes of storage. About how many songs can the larger media player hold?

Know Need Plan Know Need Plan

A portable media player has 2 gigabytes of storage and can hold about 500 songs. A similar but larger media player has 80 gigabytes of storage. About how many songs can the larger media player hold?

A portable media player has 2 gigabytes of storage and can hold about 500 songs. A similar but larger media player has 80 gigabytes of storage. About how many songs can the larger media player hold?

2 gigabytes holds 500 songs

Larger player has 80 gigabytes

Know Need Plan The number of songs the larger player holds

Know Need Plan Write a proportion and solve.

2x = 500(80)

2x = 40,0002x = 40,0002 2

x = 20,000

The larger media player holds 20,000 songs

A portable media player has 2 gigabytes of storage and can hold about 500 songs. A similar but larger media player has 80 gigabytes of storage. About how many songs can the larger media player hold?

homework

• Pg 127: 10-40 evens, 51, 52

• Note: showing work is optional through 24, required past that.