[Music] today we're going to estimate sums and differences in chapter 1 we learned how to round now that we're on addition and subtraction we're going to be estimating and rounding some addition and subtraction problems so my instructions say to round to the nearest 100 so I'm going to round each of these two numbers to the hundreds so 6,000 287 deciding if that two is going to stay the same or if it's going to go up to a three since the number after it's five or higher it will go up to a three so that rounds to 6,300 our second number the 100 is a six number after it is a four or less so the six will stay the same so I will have 2,600 now we can just use Mental Math like we did earlier and I can add these and get 8,900 so all we're doing today is combining two skills we've already worked on rounding and adding mentally my second example problem estimate round to the nearest thousand make sure you read the instructions carefully so you know where you're rounding to so same thing we're rounding to the thousands so I'm going to decide if our thousand's place will stay the same or if we'll go up one so that Eight's going to stay the same and this three is going to go up to a four this is subtraction it's another thing you need to watch out for if we're adding or subtracting so this be 0 0 Z 8 subtract 4 is four 9 subtract 6 is three there we go so since these are two skills we've already worked on and hopefully you've mastered I think we're ready to already jump in and have you do two practice problems are three actually so estimate round each number to the nearest thousand so you're going to have three practice problems you're going to round each of them to the thousands and make sure you double check to see if you're adding or subtracting go ahead and pause it and then unpause it to check your work okay the first practice problem I don't have room to show all my work on this one but the first number is going to change to 5,000 the second number is going to stay at 2,000 so 5,000 + 2,000 is 7,000 our second problem our first number is going to stay at 12,000 then we're going to subtract 9,000 so that will equal 3,000 and our third practice problem our first number is going to round up to 77,000 our second number will stay a two at 12,000 so 77,000 + 12,000 = 89,000 and now we're ready for the three problems we'll check in class tomorrow same instructions except we're rounding each number to the nearest 100 this time and we have three problems again number one 197 + 653 number two 3,456 + 4,321 and your last problem today is 8,649 subtract 5,718 thank you for listening and have a glorious day [Music]