Continuing with our unit on whole numbers, we started talking about rounding and estimation this week. The first strategy we learned was rounding using benchmarks. Students were asked to underline the benchmark they need to round to, all numbers before this stay the same, all numbers after become zeros, and the underlined number will either round up or down. So for example:
Round the number 234 567 to the:
nearest ten thousands- 230 000 because 34 000 is between 40 000 and 30 000 but would round down.
nearest thousands- 235 000 because 4 500 is between 4 000 and 5 000 but would round up.
nearest hundreds- 234 600 because 567 is between 600 and 500 but would round up.
We also discussed front-end rounding and how it can be used as an addition strategy. If asked to solve 423 567 + 345 908, the students could first add 400 000 + 300 000 to get 700 000. The students then know that their answer has to be greater than 700 000. The students are encouraged to use number lines while learning these strategies.
This week we will continue to learn different strategies for estimation and rounding. The students will also be working on addition and subtraction of large numbers.