In this Grade 4 Saxon Math Intermediate 4 lesson, students learn how to subtract three-digit numbers with regrouping by exchanging tens for ones and hundreds for tens when the top digit is smaller than the bottom digit. The lesson also covers subtracting money amounts in decimal form by aligning decimal points and regrouping across place values. Students practice estimation using compatible numbers alongside standard subtraction algorithms.
Section 1
📘 Subtracting Three-Digit Numbers with Regrouping
When subtracting, we sometimes need to regroup. To do this, we exchange 1 ten for 10 ones, or 1 hundred for 10 tens.
Next, you’ll apply this regrouping technique to find differences like and solve problems involving money.
Section 2
Subtracting With Regrouping
When you can't subtract in one column because the top digit is smaller, you must regroup or 'borrow'. You exchange 1 from the next higher place value for 10 of the current place value, like trading 1 ten for 10 ones.
Find .
Borrow from the tens place for the ones, then from the hundreds place for the tens.
Find . First, borrow from the 4 to make 13 ones. Then, borrow from the 5 to make 13 tens.
Section 3
Subtracting Dollars And Cents
To subtract money, you subtract pennies, then dimes, and then dollars. The most important rule is to always line up the decimal points before you begin!
Find . Align the decimals, then borrow a dime to make ten pennies.
, so the answer is 3.05 dollars.
Olivia has 8.50 dollars and spends 3.75 dollars. How much is left?
, so she has 4.75 dollars left.
Subtracting money is just like any other subtraction, but you have to be a bodyguard for the decimal point, making sure it never moves! Line up the decimals perfectly, then subtract from right to left, starting with the pennies. If you're short on dimes, just borrow from the dollars column next door. It’s all about keeping your cents in order!
Section 4
Estimating With Friendly Numbers
Use compatible, or 'friendly,' numbers to estimate a subtraction problem. This means rounding the numbers to values that are easy to work with in your head, such as multiples of 10 or 50.
Estimate . Round to the nearest fifty cents: .
Estimate the difference between 782 and 329. Round to the nearest ten: .
Is 400 a reasonable estimate for ? Rounding gives . Yes, that's a very reasonable estimate!
Why wrestle with a tricky problem like when you can solve something easier? Estimation lets you trade those numbers for 'friendly' ones, like . This gives you a super-fast, ballpark answer of 500. It’s the perfect way to make a quick guess or to check if your detailed calculation has gone completely wild and is off track.
Book overview
Jump across lessons in the current chapter without opening the full course modal.
Continue this chapter
Expand to review the lesson summary and core properties.
Section 1
📘 Subtracting Three-Digit Numbers with Regrouping
When subtracting, we sometimes need to regroup. To do this, we exchange 1 ten for 10 ones, or 1 hundred for 10 tens.
Next, you’ll apply this regrouping technique to find differences like and solve problems involving money.
Section 2
Subtracting With Regrouping
When you can't subtract in one column because the top digit is smaller, you must regroup or 'borrow'. You exchange 1 from the next higher place value for 10 of the current place value, like trading 1 ten for 10 ones.
Find .
Borrow from the tens place for the ones, then from the hundreds place for the tens.
Find . First, borrow from the 4 to make 13 ones. Then, borrow from the 5 to make 13 tens.
Section 3
Subtracting Dollars And Cents
To subtract money, you subtract pennies, then dimes, and then dollars. The most important rule is to always line up the decimal points before you begin!
Find . Align the decimals, then borrow a dime to make ten pennies.
, so the answer is 3.05 dollars.
Olivia has 8.50 dollars and spends 3.75 dollars. How much is left?
, so she has 4.75 dollars left.
Subtracting money is just like any other subtraction, but you have to be a bodyguard for the decimal point, making sure it never moves! Line up the decimals perfectly, then subtract from right to left, starting with the pennies. If you're short on dimes, just borrow from the dollars column next door. It’s all about keeping your cents in order!
Section 4
Estimating With Friendly Numbers
Use compatible, or 'friendly,' numbers to estimate a subtraction problem. This means rounding the numbers to values that are easy to work with in your head, such as multiples of 10 or 50.
Estimate . Round to the nearest fifty cents: .
Estimate the difference between 782 and 329. Round to the nearest ten: .
Is 400 a reasonable estimate for ? Rounding gives . Yes, that's a very reasonable estimate!
Why wrestle with a tricky problem like when you can solve something easier? Estimation lets you trade those numbers for 'friendly' ones, like . This gives you a super-fast, ballpark answer of 500. It’s the perfect way to make a quick guess or to check if your detailed calculation has gone completely wild and is off track.
Book overview
Jump across lessons in the current chapter without opening the full course modal.
Continue this chapter