Teaching rounding can be intimidating. But I have found that if I teach rounding in conjunction with number lines and if I precede it with place value, my learners understand the concept and rounding is a lot easier for students to understand without all the little rhymes. I was grateful that Mr. Elementary Math had a rounding resource that easily fit into my plans.
So I first introduced number lines, by leading a discussion with three main topics:
1. What does a number line look like?
Our ideas: straight, hash marks, benchmarks/landmarks/mileposts or whatever terms you use to designate the intervals, numbers, counting up, etc. We talk about place value of tens and hundreds and how they are represented on a number line.
2. What do we use a number line for?
Our ideas: adding/subtracting, patterns, counting, measuring, multiplying/dividing, estimating, comparing/ordering
3. What are some real-life number lines?
Our ideas: rulers, yardsticks, measuring tapes, time lines, and football field markers
Our next discussion:
1. Why do we estimate?
Our ideas: to check our answer or a calculator’s answer, to come up with a quick answer, when we don’t have the tools we need to figure out an exact answer, when we don’t need to find an exact answer
2. How do we estimate?
Our ideas: truncate numbers, go to closest place value/benchmark number or rounding. I emphasize that it’s quick to add 40 + 10, versus 48 + 13. So this reinforces our place value learning.
3. What is rounding?
Our ideas: going to the closest benchmark number (tens, hundreds, thousands)
At this point, we then color-coded the rest of the 1-100 number line to help us see the closest number.
We used these number lines to do the other activity sheets in Mr. Elementary Math’s resource.
The most favorite activity is the Rounding Face Off game. Each student has a stack of numbered cards and when the game master says “go” they look at the top card and put it on the appropriate benchmark number. And whoever places the card first on the right spot, collects both cards. Lots of fun!