OA4-13 Rounding on a Number Line

Transcription

1 OA4-13 Rounding on a Number Line 1. Draw an arrow to show whether the circled number is closer to 0 or c) d) Which one-digit numbers are closer to 0? Which one-digit numbers are closer to 10? c) Why is 5 a special case? 3. Draw an arrow to show if you would round to 10 or 20 or c) Draw an arrow to show which multiple of 10 the number in the circle is closest to Circle the correct answer. Use the number lines in Questions 3 and 4 to help. 27 is closer to: 20 or is closer to: 20 or 30 c) 19 is closer to: 10 or 20 d) 13 is closer to: 10 or 20 e) 26 is closer to: 20 or 30 f) 12 is closer to: 10 or 20 g) 251 is closer to: 250 or 260 h) 258 is closer to: 250 or 260 i) 333 is closer to: 330 or 340 j) 339 is closer to: 330 or Operations and Algebraic Thinking 4-13

2 6. Draw an arrow to the nearest ten, then round each number to the nearest ten c) d) e) Circle the correct answer. Then round the number to the nearest ten. 27 is closer to 20 or is closer to 10 or 20. Round to 30. Round to. c) 39 is closer to 30 or 40. d) 31 is closer to 30 or 40. Round to. Round to. e) 62 is closer to 60 or 70. f) 251 is closer to 250 or 260. Round to. Round to. g) 348 is closer to 340 or 350. h) 258 is closer to 250 or 260. Round to. Round to. i) 341 is closer to 340 or 350. j) 256 is closer to 250 or 260. Round to. Round to. Operations and Algebraic Thinking

3 OA4-14 Rounding on a Number Line (Hundreds and Thousands) 1. Draw an arrow to show whether the circled number is closer to 0 or c) d) Is 50 closer to 0 or to 100? Why is 50 a special case? 3. Would you round to 0 or 100? Round 80 to: 0 or 100 Round 40 to: 0 or 100 c) Round 10 to: 0 or 100 d) Round 60 to: 0 or Draw an arrow to show which hundred you would round to Circle the correct answer. 153 is closer to: 100 or is closer to: 100 or 200 c) 117 is closer to: 100 or 200 d) 135 is closer to: 100 or 200 e) 370 is closer to: 300 or 400 f) 332 is closer to: 300 or 400 BONUS Show the approximate position of each number on the line. What hundred would you round to? c) 687 d) Operations and Algebraic Thinking 4-14

4 6. Draw an arrow to show whether the circled number is closer to 0 or 1, , ,000 c) ,000 d) , Is 500 closer to 0 or 1,000? Why is 500 a special case? 8. Circle the correct answer. 100 is closer to: 0 or 1, is closer to: 0 or 1,000 c) 600 is closer to: 0 or 1,000 d) 400 is closer to: 0 or 1, Draw an arrow to show which thousand you would round to. 1,000 1,100 1,200 1,300 1,400 1,500 1,600 1,700 1,800 1,900 2,000 1,217 1,847 6,000 6,100 6,200 6,300 6,400 6,500 6,600 6,700 6,800 6,900 7,000 6,348 6, Circle the correct answer. 1,953 is closer to: 1,000 or 2,000 3,487 is closer to: 3,000 or 4,000 c) 6,293 is closer to: 6,000 or 7,000 d) 8,612 is closer to: 8,000 or 9,000 e) 5,521 is closer to: 5,000 or 6,000 f) 3,190 is closer to: 3,000 or 4, Write a rule for rounding a four-digit number to the nearest thousand. Operations and Algebraic Thinking

5 OA4-15 Rounding To round to the nearest ten, look at the ones digit. 0, 1, 2, 3, or 4 you 5, 6, 7, 8, or 9 you 1. Round to the nearest ten c) 72 d) 66 e) 81 f) 93 g) 14 h) 59 i) Round to the nearest ten. Underline the tens digit first. Then put your pencil on the digit to the right (the ones digit). This digit tells you whether to or down c) 320 d) 255 e) 784 f) 667 g) 441 h) 939 i) 316 j) 520 k) 985 l) 534 m) 758 n) 845 o) 293 To round to the nearest hundred, look at the tens digit. 0, 1, 2, 3, or 4 you 5, 6, 7, 8, or 9 you Example: 345. The 4 tells you to, so round 345 to Round to the nearest hundred. Underline the hundreds digit first. Then put your pencil on the digit to the right (the tens digit) c) 650 d) 170 e) 240 f) 620 g) 710 h) 580 i) 980 j) 930 k) 750 l) 290 m) 851 n) 158 o) 338 p) 411 q) 658 r) 149 s) 291 t) 372 u) 868 v) 207 w) 525 x) Operations and Algebraic Thinking 4-15

6 To round 2,531 to the nearest hundred, underline the hundreds digit: 2,531 Then look at the tens digit. The 3 tells you to : 2, Round to the nearest hundred. Underline the hundreds digit first. Then put your pencil on the digit to the right (the tens digit). 2,156 2,200 4,389 c) 3,229 d) 1,905 e) 5,251 f) 9,127 g) 6,472 h) 8,783 i) 7,255 j) 1,098 k) 3,886 l) 4,624 m) 8,077 n) 6,382 o) 9,561 p) 2,612 q) 5,924 BONUS r) 2,963 s) 997 t) 3,982 To round to the nearest thousand, look at the hundreds digit. 0, 1, 2, 3, or 4 you 5, 6, 7, 8, or 9 you Example: 7,826. The 8 tells you to, so round 7,826 to 8, Round to the nearest thousand. Underline the thousands digit first. Then put your pencil on the digit to the right (the hundreds digit). 2,757 3,000 9,052 c) 6,831 d) 3,480 e) 5,543 f) 4,740 g) 8,193 h) 2,607 i) 6,107 j) 9,125 k) 5,114 l) 7,649 m) 1,336 n) 9,538 o) 4,226 p) 7,311 q) 28,644 r) 32,750 s) 79,928 t) 91,347 u) 67,812 Operations and Algebraic Thinking

7 OA4-16 Rounding on a Grid 1. Underline the digit you want to round to. Then say whether you would round up or down. hundreds hundreds c) hundreds d) tens e) tens f) thousands g) thousands h) ten thousands i) ten thousands To round to the underlined digit: Step 1: Decide whether to or down Step 2: To, add 1 to the digit. To, keep the digit the same Step 3: The digits to the right of the rounded digits become 0. The digits to the left remain the same Round each number to the given digit. thousands thousands c) hundreds (ru) () ru ru d) hundreds e) tens f) tens ru ru ru 86 Operations and Algebraic Thinking 4-16

8 g) hundreds h) tens i) tens ru ru ru j) thousands k) ten thousands l) hundreds ru ru ru m) hundreds n) tens o) ten thousands ru ru ru If you need to round the digit 9 up, you will have to regroup. Example: Round 3,995 to the nearest hundred rounds up to 1,000 Regroup the 10 hundreds Complete the rounding. as 1 thousand and add it to the 3 thousands. 3. Round each number to the underlined place value. You will need to regroup. 2,195 3,982 c) 13,296 d) 46,981 e) 395,321 f) 729,893 g) 74,399 h) 604, Round each number to the underlined place value (regroup if necessary). 3,192 39,621 c) 13,291 d) 9,723 e) 9,423 f) 349,423 g) 479,723 h) 395, Round each number to the nearest ten thousand. 492, ,306 c) 809,312 d) 849,312 Operations and Algebraic Thinking

9 OA4-17 Estimating Sums and Differences Mathematicians use the sign to mean approximately equal to. 1. Estimate by rounding to the nearest ten c) 47 d) e) f) g) h) = 40 = = = i) j) k) l) = = = = 2. Estimate by rounding to the nearest hundred c) 470 d) e) f) g) h) = = = = i) j) k) l) Estimate by rounding to the nearest thousand. 1,275 1,000 4,729 c) 2,570 d) 39, , , , , , Round each number to the nearest hundred. Then find the sum or difference. 3, ,235 3,581 1,826 c) 4,821 3, Operations and Algebraic Thinking 4-17

10 5. Mumtaz collected 75 books for charity and Elizabeth collected 18 books. About how many did they collect altogether? 6. Class 4A collected 287 books and class 4B collected 476 books for charity. About how many books did 4A and 4B collect altogether? Is your estimate higher or lower than the actual answer? How do you know? 7. A store has the following items for sale: Sofa $472 Armchair $227 Table $189 Desk $382 Lamp $112 What could you buy if you had $800 to spend? Estimate to find out. Then add the actual prices to check your estimate. 8. Daniel estimates as = 900. Calculate the actual sum. Is Daniel s estimate higher or lower than the actual sum? Why does this make sense? 9. Maya adds numbers. Use estimation to decide whether her answers are reasonable = 1,021 3, ,209 = 7,725 c) 2, ,351 = 4, Round the number to each place value given (regroup if necessary). 3,485 Tens Hundreds Thousands 8,502 BONUS BONUS 9,697 Write every number that satisfies all three statements. When rounded to the nearest ten, it is 6,500. When rounded to the nearest hundred, it is 6,500. When rounded to the nearest thousand, it is 6,000. BONUS The estimated difference between two numbers is 400. What might the original numbers be? Operations and Algebraic Thinking