Name: ___________________________________ Date: ____________ Module 1: DECIMALS Lesson 4: Rounding Decimals Rounding Decimals Place value can help you understand and
write and compare decimal numbers. Rounding Decimals Rounding Decimals Caution! Look at the digit to the right of the place to which you are rounding. If it is 5 or greater, round up. If it is less than 5, round down.
Rounding Decimals Rounding Decimals to Estimate Sums and Differences Estimate by rounding to the indicated place value. A. 7.13 + 4.68; ones 7.13 + 4.68 Round to the nearest whole number. 7 + 5 = 12 The sum is about 12. B. 9.705 0.2683; tenths
9.705 9.7 0.2683 0.3 9.4 Round to the tenths. Align. Subtract.
Rounding Decimals Example Estimate by rounding to the indicated place value. 6.09 + 3.72; ones 6 + 4 = 10 Rounding Decimals Remember! Compatible numbers are close to the numbers that are in the problem and are helpful when you
are solving the problem mentally. Ex. 34.5 -> 2.95 -> 35 3 Rounding Decimals Using Compatible Numbers to Estimate Products and Quotients Estimate each product or quotient. A. 33.83 1.98
35 2 = 70 35 and 2 are compatible. So 33.83 1.98 is about 70. B. 72.77 26.14 75 25 = 3 75 and 25 are compatible. So, 72.77 26.14 is about 3.
Rounding Decimals Example Estimate each product or quotient. 62.31 18.52 60 20 = 3 Rounding Decimals You can also use front-end estimation to estimate with decimals. Front-end estimation means to use only the whole-number part of the decimal.
Rounding Decimals Using Front-End Estimation Estimate a range for the sum. 7.86 + 36.97 + 5.40 Use front-end estimation. 7.86 7 36.97
36 5.40 + 5 at least 48 Add the whole numbers only. The whole-number values of the decimals are less than the actual numbers, so the answer is an
underestimate. The exact answer of 7.86 + 36.97 + 5.40 is greater than 48. Rounding Decimals Example - Continued You can estimate a range for the sum by adjusting the decimal part of the numbers. Round the decimals up to 0.5 or 1. 0.86 0.97
0.40 Add the adjusted decimal part of 1.00 the numbers. 1.00 Add the whole-number estimate + 0.50 and this sum. 2.50 The adjusted decimals are greater than the actual 48.00 + 2.50 = 50.50 decimal, so 50.50 is an
overestimate. The estimated range for the sum is from 48.00 to 50.50. Rounding Decimals Check It Out Estimate a range for the sum. 8.92 + 47.88 + 3.41 underestimate: 8 + 47 + 3 = 58 overestimate: 9 + 48 + 3.5 = 60.5 from 58.00 to 60.50 Rounding Decimals
Lesson Quiz Estimate by rounding to the indicated place value. 1. 3.07442 + 1.352; tenths 4.5 2. 7.305 4.12689; nearest whole number 3 Estimate each product or quotient. 3. 6.75 1.82 14 4. 10.5 3.42 3 5. The snowfall in December, January, and February was 18.26 cm, 29.36 cm, and 32.87 cm, respectively.
About how many total centimeters of snow fell during 80 cm the three months? Rounding Decimals Student Response Systems 1. Estimate by rounding to the indicated place value. 5.891+9.326; hundredths A. 14.21 B. 14.22 C. 15.21
D. 15.22 Rounding Decimals Student Response Systems 2. Estimate by rounding to the indicated place value. 29.35-17.92; nearest whole number A. 10 B. 11 C. 12 D. 13
Rounding Decimals Student Response Systems 3. Identify the estimate of the product of 16.77 3.81. A. 48 B. 51 C. 64 D. 68 Rounding Decimals Student Response Systems 4. Identify the estimate of the quotient of
17.43 3.91. A. 6 B. 5 C. 4 D. 3 Rounding Decimals Student Response Systems 5. The weight of three students in a class are 48.23 pounds, 54.81 pounds, and 45.3 pounds. Identify the total weight of the students.
A. 130 lb B. 140 lb C. 150 lb D. 160 lb