Add within 100
Watching tens join tens and ones join ones helps your child see what really happens when numbers are added, and that is the thinking behind every written method for larger numbers. A child who understands why 36 + 7 makes a new ten will find adding two-digit numbers in 2nd grade, and three-digit numbers soon after, sensible rather than mysterious. It also makes everyday sums, like adding up two prices, possible in their head.
In this video, your child will learn to add within one hundred.
The lesson stops at each question for your child's answer.
Three problems, each a little harder
Each problem is worked step by step. Your child will solve the last one before Bobby shows how.
Example 1
42 + 30 = ?
Example 2
47 + 6 = ?
Your child's turn
36 + 27 = ?
The three key steps
- 1Add the ones, then add the tens.
- 2Ten ones make one ten.
- 3Add the new ten with the tens.
Mistakes to listen for
- Lining the 7 up under the 3 in 36 + 7, adding it to the tens, and getting 106 instead of 43.
- Writing down all 13 ones instead of making a new ten, so 36 + 7 becomes 313 or 3013.
- Treating 36 + 20 like 36 + 2 and answering 38, because the zero in 20 seems unimportant.
The lesson shows every step, so your child sees why it works. Read our parent's guide to adding two-digit numbers within 100 →
Is your child ready to practice what they've learned?
Bobby's Math Club offers unlimited practice for free.
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More 1st grade Numbers & Place Value, with questions your child answers along the way.
Questions parents ask
Does my child need an account to watch?
No. You can watch this on any device at any time. If your child would like to practice adding two-digit numbers within 100, and you'd like parent-friendly reports on your child's progress and growth, you can join Bobby's Math Club for unlimited free practice.
What happens when my child answers a question?
A right answer gets a cheer, and the lesson carries on. If your child isn't sure, they can tap "I don't know yet", and Bobby gives the answer and shows another example. Nothing is scored or stored.
Is this the same lesson that's on YouTube?
Yes. Here, the lesson stops at each question and waits for your child to answer. On YouTube, each question stays on screen for a few seconds, and then the lesson plays on.
Where can I learn more?
There's a short, kid-friendly lesson like this one for every Pre-K to 5th grade math skill, all in our video library. Our parent's guide to adding two-digit numbers within 100 has more on where kids get stuck and how you can help at home. In the club, your child practices at just the right level, about five minutes a day, and you get parent-friendly reports as they grow. Learn more about how it works →
Practice adding two-digit numbers within 100
Questions at your child's level, about five minutes a day, on adding two-digit numbers within 100 and whatever PK-5 skills they need to develop. Unlimited practice, free forever.
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