Video:Two-Digit Addition By Grouping

Transcript:Two-Digit Addition By Grouping

Hi, my name is Bassem Saad, I am an associate math instructor and a Ph.D. candidate. I'm here today for About.com to show you how to do two-digit addition with regrouping.

Add the First Digits for Two-Digit Addition By Grouping

So, recall that a digit is any number from zero to nine and whenever we add two-digit numbers, we want to work from right to left. So say we want to add 35 to 17 -- we have a three-step process. The first step, we want to add the first digit of the first number to the first digit of the second number. So that's five plus seven, but we get 12 -- it's a two-digit number.

Carry the Extra Digit for Two-Digit Addition By Grouping

Well we record the first digit, the two, immediately underneath the five and seven. The second step, we still have this one to worry about. We want to carry the second digit of the sum, in other words this one, and place it above the second digit of the first number. So the one goes right up here above the three.

Add the Second Digits for Two-Digit Addition By Grouping

Step three, we want to add all three numbers in the second digit place, so that is one, three, and one. So one, plus three, plus one, equals five. And we place the five underneath the one in the second digit place. So now we know that 35 plus 17 is 52. So let's take a look at one more example.

Another Example of Two-Digit Addition By Grouping

Say we want to add 59 plus 33. Well, according to our first step we just add the nine and three. Nine plus three equals 12, and we can record the two just underneath the nine and the three. The second step tells us we have to carry this one from the 12 all the way up here, above the five. And then in the third step we want to add all the second digits.

Finish the Two-Digit Addition By Grouping

So that is one, plus five, plus three. So one, plus five, plus three, equals nine. We record this nine underneath the three. So 59 plus 33 is 92. So we now we know how to do two-digit addition with regrouping.

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