Welcome to addition and subtraction within one hundred. This means we work with numbers from zero to one hundred. Let's start with simple addition. Twenty-three plus fifteen equals thirty-eight. We can visualize this with dots - blue dots for twenty-three, red dots for fifteen, and green dots showing the total of thirty-eight.
Now let's learn addition with carrying. When adding digits and the sum is ten or more, we carry over to the next place. For example, forty-seven plus thirty-six. First, add the ones place: seven plus six equals thirteen. Write down three and carry one to the tens place. Then add the tens place: four plus three plus the carried one equals eight. So forty-seven plus thirty-six equals eighty-three.
Now let's learn subtraction within one hundred. Subtraction means taking away numbers from a larger number. For example, eighty-five minus twenty-three equals sixty-two. We can visualize this by starting with eighty-five blue dots, crossing out twenty-three of them, and counting the remaining sixty-two green dots.
Now let's learn subtraction with borrowing. When the top digit is smaller than the bottom digit, we need to borrow from the tens place. For example, sixty-two minus twenty-eight. Since two is less than eight, we borrow one from the tens place. This makes the six become five, and the two becomes twelve. Now twelve minus eight equals four in the ones place, and five minus two equals three in the tens place. So sixty-two minus twenty-eight equals thirty-four.
To summarize what we have learned about addition and subtraction within one hundred: We work with numbers from zero to one hundred. We use carrying when adding digits and their sum is ten or more. We use borrowing when the top digit is smaller than the bottom digit in subtraction. These fundamental skills help us solve everyday math problems.