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Lesson 4: Basic Addition (Part 2 of 2)
Don't forget to watch the embedded YouTube video clip for this lesson at the bottom of the page.
Look at problem 3. Adding the ones column is easy. 3 + 1 is 4. To add the tens column, we add 4 + 9, and get 13. Again, we cannot fit two digits into a column. What we must do is write the 3 of 13 below the line in the 10s column. We have to carry the one into the hundreds column to the left, even though there is nothing else there. We can then bring the 1 down below the line to represent 100, and the final answer is 134.
Make sure you understand what is really happening here in the tens column. The 4 really means 40, since it's four 10s. The 9 is really 90, since it's nine 10s. When we add 40 + 90, we get 130, but we need to put some answer in the 10s column. How can we break 130 into tens and hundreds? There is one 100, and three 10s. Just like with the 1s column, we have to put the 3 tens below the line, and carry the one hundred into the next column. This is a bit tricky to understand, but try to think about it. Each column works the same way. We write the portion of the answer that we can in that column, and then carry over the rest to the column to the left.
Take a look at problem 4. Here we have to carry into both the tens and the hundreds column. Remember to always add the columns from right to left, starting with the ones column. See if you can understand how the problem was solved. In the tens column, we actually had to add three numbers--the two that were part of the problem, and the 1 that we carried.
Make sure that you fully understand how adding works. It is one of the most fundamental topics in math, and it will come up again and again.
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