Warm Up Problems Round each decimal to the nearest whole number. 1) 4.75 2) 34.1 3) 22.48

Estimate Products Lesson 3-2

Objectives I can estimate the product of two decimal numbers. I can explain my reasoning after solving a problem.

Rounding - Notes First underline the digit to be rounded. Look at the digit to the right. If the digit is 4 or less, keep the underlined digit the same. If the digit is 5 or higher, add 1 to the underlined digit. After rounding, all place values to the right of the underlined digit are zero.

Example 1 - Notes Estimate 8.7 x 2.8. Round to the nearest whole number. 8.7 ~ 9 2.8 ~ 3 9 x 3 = 27 So the product is about 27.

Example 2 - Notes Estimate 42.6 x 37.2. Round to the greatest place value to make it easier to compute mentally. In this case the tens place. 42.6 ~ 40 37.2 ~ 40 40 x 40 = 1,600 So the product is about 1,600.

Example 1 and 2 – Guided Practice Estimate each product. 1) 9.6 X 1.8 2) 68.4 x 21.3

Example 3 - Notes A greyhound can travel 39.3 miles per hour. At this speed, about how far could a greyhound travel in 6.5 hours? 39.3 ~ 40 6.5 ~ 7 40 x 7 = 280. So, about 280 miles.

Example 4 - Notes Suppose one U.S. dollar is equal to 5.8 Egyptian pounds. About how many Egyptian pounds could you receive for $48.50? 5.8 ~ 6 48.5 ~ 50 50 x 6 = 300 So, it would be about 300 Egyptian pounds.

Example 3 and 4 – Guided Practice 3) Earth is rotating around the Sun about 18.6 miles per second. About how many miles does it travel in 4.8 seconds? 4) A King Palm can grow about 2.1 feet per year. Estimate the height of the King Palm, in yards, after 15 years.

Example 5 - Notes Patrice has $20 to buy binders. Binders cost $4.29 each. Does she have enough money? Explain your reasoning. Estimate: $4 x 5 = $20 $5 x 5 = $25 The actual price is somewhere in between $20 and $25, so she does not have enough money.