Estimating adding and subtracting 3 digit numbers

TL;DR

Practice estimating addition and subtraction of three-digit numbers by rounding to the nearest 10 or 100.

Transcript

• [Instructor] What we're going to do in this video is get some practice estimating adding and subtracting three digit numbers and so here it says 398 plus 251 is, and this squiggly equal sign means we just need to make an estimate. We wanna know what is this roughly equal to? So normally I say pause the video but here I want you to work it out in ... Read More

Key Insights

• 🛝 Estimating addition and subtraction involves rounding numbers to the nearest 10 or 100 for quick calculations.
• 🛟 Estimation is useful in real-life situations, such as shopping, where quick approximate totals are needed.
• 🛝 Different rounding techniques, such as rounding to the nearest 10 or 100, can yield similar estimations.

Questions & Answers

Q: How can we estimate the sum of 398 and 251?

One way to estimate the sum is to round 398 to the nearest 100 (which is 400) and round 251 to the nearest 10 (which is 250). Adding them up gives us an estimate of around 650.

Q: What is the purpose of estimation in everyday life?

Estimation is useful when you want to quickly calculate approximate totals, such as when shopping. It allows you to get an idea of the cost without needing to find the exact answer.

Q: How can we estimate the difference between 678 and 273?

One method is to round 678 to the nearest 100 (which is 700) and round 273 to the nearest 100 (which is 300). Subtracting them gives us an estimate of around 400.

Q: Why might multiple choice questions be used for estimation?

Since different individuals may make slightly different estimations, multiple choice options provide a range of reasonable estimates. The correct choice should be the one closest to any reasonable estimate.

Summary & Key Takeaways

• In this video, the instructor explains how to estimate the sum of 398 and 251 by rounding to the nearest 10 or 100.

• The instructor also demonstrates how to estimate the difference between 678 and 273 using the same rounding techniques.

• Estimation is a useful skill in everyday life, especially when shopping and calculating approximate totals.