Lesson 9 Rounding to any digit

Your lesson goal is: By the end of this lesson you will be able to round a number to any place value. You will be able to complete this without using a number line.

Let’s try a few problems! For the first problem we will round 4,333 to the nearest thousand. Between what two thousands is 4,333?

Problem # 1 4,333 is between 4,000 and 5,000.

Problem # 1 4,333 is between 4,000 and 5,000. What number is halfway between 4,000 and 5,000?

Problem # 1 4,500 is midway between 4,000 and 5,000.

Problem # 1 4,500 is midway between 4,000 and 5,000. So is 4,333 less than or more than halfway?

Problem # 1 It is less than halfway.

Problem # 1 It is less than halfway. Would you round up to 5,000 or round down to 4,000?

Problem # 1 Your answer should be 4,333 ≈ 4,000.

Problem # 2 Let’s try another problem. Let’s round 65,000 to the nearest ten thousand.

Problem # 2 Let’s round 65,000 to the nearest ten thousand.

Problem # 2 Let’s round 65,000 to the nearest ten thousand. What two ten thousands is 65,000 between?

Problem # 2 Did you get that 65,000 is between 60,000 and 70,000?

Problem # 2 Did you get that 65,000 is between 60,000 and 70,000? What number is midway between 60,000 and 70,000?

Problem # 2 That’s right! 65,000 is. Wait that is the number we are rounding. Do you remember what we need to do?

Problem # 2 Because 65,000 is the midpoint, we will round it up. So 65,000 ≈ 70,000.

Problem # 3 147,591 ≈ ? Whisper this number to someone at your table.

Problem # 3 What hundred thousand would you round 147,591 to?

Problem # 3 What hundred thousand would you round 147,591 to? Did you say 100,000?

Problem # 3 What would happen if you rounded 147,591 to the nearest ten thousand?

Problem # 3 What would happen if you rounded 147,591 to the nearest ten thousand? Did you get 150,000?

Problem # 3 What would happen if you rounded 147,591 to the nearest thousand?

Problem # 3 What would happen if you rounded 147,591 to the nearest thousand? Did you get 148,000?

Problem # 3 What happens to our estimate as we round to smaller place values?

Problem # 3 When would we want to use a bigger estimate? What about a smaller estimate? Talk about this as table groups.

Time for some Practice! Please complete problems 1A, 1D, 2B, 2C, 3A, 3C, 3E and 4B on pages 49 and 50 in your math book.