Rounding is an important math skill that is difficult for some students to really get. There are some great songs, rhymes, and “tricks” to help students memorize rounding rules. However, it is important make sure students engage in activities to help them understand the meaning of rounding before the tricks. Really understanding the meaning helps them to remember the rules later and apply estimating skills in different situations. It also helps to build a stronger number sense and understanding of how mathematics works.
Have students work with partners to build a tower of 10 with base ten blocks or Legos. Then make another tower with 20 Legos, and a third with 13. Ask your students to put the towers in order and compare the 13 tower with the 10 tower and the 20 tower. Which tower is the 13 closer to in size, the 10 or 20? Ask them how they can tell which one is bigger. Use this as an opportunity to discuss the meaning of “about”, “estimate”, and “round”. Try again a few times with other numbers. While students are working hands on, continue to explain rounding using math vocabulary.
Give students a hundred chart and ask them to skip count by 10 starting with zero. Next give them a number like 34 and have them find that number on the chart. Have them use the chart to discuss if 34 is closer to 30 or 40. Ask questions, use vocabulary and explain rounding using the chart. Continue with a few more numbers and ask students to explain patterns they are finding with rounding.
Next, you can cut the hundred chart apart and tape it together like a number line. This takes a little time, so you could make one ahead of time if you wanted. Work with the students using the number line to round numbers to the nearest ten. You can also use printed number lines or have students draw number lines on notebook paper.
Take your students outside and have them draw number lines on the hard top with sidewalk chalk. Give them numbers and let them jump around on the number line to the nearest ten or hundred.
Use painters tape to make a number line on your floor. Give students numbers on index cards and have them find their number then round.