Before understanding how to add big numbers, you need to understand place value. Place value is just a way of separating digits of bigger numbers. This concept will be reused a lot throughout all of addition, and even expands to decimals.
ISAIAH LOPEZ
Place value is just how we group different digits when adding them. In order to add big numbers, we need to make sure we add the right digits together, because some of them actually mean something different. For example, in the number 23, the 3 is in the ones place, so its value is still 3. The 2, however, is actually in the tens place. This means that its value is actually 20. If we add 20 and 3, we get 23, but if we add 2 and 3, we get 5. Notice how different place values can cause different answers. Let's do another example. In the number 3,572, the 2 is in the ones place, so it is worth 2. The 7 is in the tens place, so it is worth 70. The 5 is in the hundreds place, so it is worth 500. The 3 is in the thousands place, so it is worth 3,000. Once we get to the thousands place, we usually separate it with a comma.