2. Estimating with Whole Numbers Definitions: Compatible Numbers – Are numbers that are close to the actual numbers in a math problem. Estimate - Is an answer that is close to the exact answer and is found by rounding. Underestimate – An estimate that is less than the exact answer. Overestimate - A estimate that is greater than the exact answer.

3. Estimating a Sum of Difference by Rounding Estimate the sum or difference by rounding to the indicated place value. Example 1: 5,439 + 7,516; thousands 5,439 5,000 + 7,516 + 8,000 13,000 The sum of 5,439 and 7,516 is approximately 13,000. Example 2: 62,167 – 47,511; ten-thousands 62,167 60,000 - 47,511 - 50,000 10,000 The difference of 62,167 and 47,511 is approximately 10,000. Strategy: 1.) Round each number to the indicated place value. 2.) Apply the indicated operation.

4. Estimating a Sum of Difference by Rounding Estimate the sum or difference by rounding to the greatest place value. Example 3: 611 + 378 611 600 + 378 + 400 1,000 The sum of 611 and 378 is approximately 1,000. Example 4: 45,709 – 11,250 45,709 50,000 - 11,250 - 10,000 40,000 The difference of 45,709 and 11,250 is approximately 40,000. Strategy: 1.) Round each number to the largest place value. 2.) Apply the indicated operation.

5. Try these: Estimate the sum or difference by rounding to the indicated place value. 1.) 11,245 + 12, 768, ten thousands2.) 581 – 354, hundreds Try these: Estimate the sum or difference by rounding to the greatest place value. 3.) 110,490 + 252,8814.) 6,611 – 4,449 Estimating a Sum of Difference by Rounding

6. Estimating with Whole Numbers Let’s try these: 1.) Ms. Escobar is planning a graduation celebration for the entire 8 th grade. There are 9 eight-grade homeroom classes of 27 students. Estimate how many cups Ms. Escobar needs to buy for the students if they all attend the celebration. 2.) Mrs. Byrd will drive 120 miles to take Becca to the state fair. She can drive 65 miles per hour. About how long will the trip take?