Subtraction is taking one number away from another to find the difference. When working with four-digit numbers, we subtract ones from ones, tens from tens, hundreds from hundreds, and thousands from thousands.
Always start subtracting from the ones place (right side) and move left to thousands place.
Word problems describe real-life situations where you need to subtract. Look for key words like "how many more," "how many less," "difference," "left," "remaining," or "take away" to know when to subtract.
Washington Elementary School has 1,245 students. Jefferson Middle School has 987 students. How many more students does Washington Elementary have?
Answer: Washington Elementary has 258 more students.
The word "more" often means you need to find the difference between two numbers using subtraction.
Regrouping (sometimes called borrowing) is needed when the top digit is smaller than the bottom digit in any place value. You borrow from the next higher place value to make the subtraction possible.
There were 3,042 people at the baseball game. After the seventh inning, 1,568 people left. How many people remained?
Answer: 1,474 people remained.
When regrouping, remember to reduce the number you borrowed from by 1 and add 10 to the number you're working with.
Comparison problems ask you to find how much larger or smaller one quantity is compared to another. You always subtract the smaller number from the larger number.
The distance from New York to Chicago is 1,283 kilometers. The distance from New York to Miami is 2,088 kilometers. How much shorter is the trip to Chicago?
Answer: The trip to Chicago is 805 kilometers shorter.
Words like "shorter," "longer," "taller," "heavier," or "lighter" often indicate comparison problems that require subtraction.
Some word problems describe situations where you start with an amount and some is taken away or used. You subtract to find what remains.
A library had 4,500 books. During a book sale, they sold 2,347 books. How many books does the library have left?
Answer: The library has 2,153 books left.
Words like "left," "remaining," "still have," or "how many are left" tell you to subtract what was used or taken away from the original amount.
You can check your subtraction by adding your answer to the number you subtracted. If you get back to the original number, your subtraction is correct.
Original problem: 2,836 - 1,592 = 1,244
Since 1,244 + 1,592 = 2,836, our subtraction is correct.
Always check your work, especially when regrouping is involved. This helps catch any mistakes in your calculations.