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Warm-Up

Warm-Up. Round to the nearest thousandth: 5.0099. Practice Rounding. Round to the nearest tenth: 5.249 Closer to 5.2 or 5.3? Round to the nearest hundredth: 5.249 Closer to 5.24 or 5.25? Round to the nearest whole: 357.82 Closer to 357 or 358? Round to the nearest hundred: 357.82

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Warm-Up

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  1. Warm-Up Round to the nearest thousandth: 5.0099

  2. Practice Rounding • Round to the nearest tenth: 5.249 • Closer to 5.2 or 5.3? • Round to the nearest hundredth: 5.249 • Closer to 5.24 or 5.25? • Round to the nearest whole: 357.82 • Closer to 357 or 358? • Round to the nearest hundred: 357.82 • Closer to 300 or 400?

  3. Practice Rounding • Round to the nearest thousandth: 5.0099 • 5.010 Must have the last 0 for the thousandths place! • Round to the nearest hundredth: 64.284 • 64.28 • Round to the nearest tenth: 10.957 • 11.0 Must have the last 0 for the tenths place!

  4. Adding and Subtracting Decimals • Same idea as with fractions: the denominator (place values) must be common. • So, 3.46 + 2.09 is really like3 + 2 ones + 4 + 0 tenths + 6 + 9 hundredths = 5.55

  5. 1 + 1 + .1 1 + .3 Multiplying Decimals • Easiest to see with the area model. • 2.1 • 1.3 • Where is 2 • 1?2 • 0.3?1 • 0.1?0.1 • 0.3?

  6. Proportions • A comparison of equal fractions • A comparison of equal rates • A comparison of equal ratios

  7. Ratios and Rates • If a : b = c : d, then a/b = c/d. • If a/b = c/d, then a : b = c : d. • Example: • 35 boys : 50 girls = 7 boys : 10 girls • 5 miles per gallon = 15 miles using 3 gallons

  8. To determine proportional situations… • Start easy: • I can buy 3 candy bars for $2.00. • So, at this rate, 6 candy bars should cost… • 9 candy bars should cost… • 30 candy bars should cost… • 1 candy bar should cost… this is called a unit rate.

  9. To determine proportional situations • Here’s another. • 7 small drinks cost as much as 5 large drinks. At this rate… • How much should 14 small drinks cost? • How much should 21 small drinks cost? • How much should 15 large drinks cost?

  10. Ratios are not the same as fractions • The ratio of males to females is 3 : 2. • That means 3/5 of the people are male, and 2/5 of the people are female. • The mixture is 3 parts water and 1 part green dye. • That means that 3/4 of the mixture is water and 1/4 of the mixture is green dye.

  11. We can add fractions, but not ratios • One group of 15 people has 2 females for every male. • Another group of 32 people has 1 female for every 3 males. • What is the ratio of females to males if the two groups combine?

  12. Exploration 6.3 • Do the questions for #1.

  13. Homework Due next Tuesday Section 5.4: 2bd, 5bdf, 8, 10ac, 16abcd, 40abc

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