Summation by parts is a way of adding up a lot of numbers. Imagine you have a big list of numbers, like 5, 7, 9, 11, 13. If you want to figure out how much the whole list adds up to, you can add them up one by one. But that can take a while if your list is really long.

Summation by parts is a faster way to add them up. Instead of adding all the numbers one by one, you divide them into two groups, and add each group up separately. For example, with this list you could break it up into two groups: the first group would be 5, 7, 9 and the second group would be 11, 13. Now you can add up each group separately, so 5+7+9 is 21 and 11+13 is 24. Then you add the two groups together, 21 plus 24 is 45, so the whole list adds up to 45.

Summation by parts is a faster way to add them up. Instead of adding all the numbers one by one, you divide them into two groups, and add each group up separately. For example, with this list you could break it up into two groups: the first group would be 5, 7, 9 and the second group would be 11, 13. Now you can add up each group separately, so 5+7+9 is 21 and 11+13 is 24. Then you add the two groups together, 21 plus 24 is 45, so the whole list adds up to 45.