yego.me
💡 Stop wasting time. Read Youtube instead of watch. Download Chrome Extension

Breaking apart 3-digit addition problems | 2nd grade | Khan Academy


3m read
·Nov 11, 2024

  • Mike isn't sure how to add 189 + 608, help Mike by choosing an addition problem that is the same as 189 + 608.

Now let's look at these choices. Let's just start with this first choice. Actually, all of these choices start with having 1 hundred; they all have 1 hundred. So where do we see 1 hundred here? Well, in 189, we have a 1 in the hundreds place. So this right over here, that is one 1 hundred, 100.

Then all of the choices actually have 6 hundreds, 6 hundreds, 6 hundreds; where are they getting that from? Well, in 608, the 6 is in the hundreds, so that 6 represents 6 hundreds, 6 hundreds. So that's where they got the 1 hundred and the 6 hundreds from.

Then all of them have 8 tens. So they're actually all looking pretty similar up to that point. They all have 8 tens, 8 tens, 8 tens; where do they get that from? Well, in 189, this 8 is in the tens place, so it represents 8 tens, 8 tens.

And then what else do they have? Well, this is where they all start to be a little bit different, so let's go one by one. So this next one then has 9 ones, 9 ones; where are they getting that from? Well, in 189, the 9 is in the ones place, so it's reasonable to write 9 ones.

And then finally, they have 8 ones. 8 ones; where do they get that from? Well, in 608, the 8 is in the ones place, so it's 8 ones. So this first choice is looking quite good.

Now you might be saying, "Okay, we took into account all of these digits, except for this 0 over here. How come we didn't? How come there's a 0 here in the tens place?" Well, that would just be 0 tens, 0 tens, which is just zero; so it's not going to change the value of this. So this first choice is indeed the same as the original addition problem.

If we want to see where the other ones break down, this one has 8 tens written twice. We only have one; we have an 8 tens here, but this 8 is in ones, so this should say "ones," right over here. And this choice, we have the 8 ones, but this 9 right over here, this is ones; this isn't tens, so this should be "ones."

So that's why we wouldn't pick either of those. Let's do another one of these, or a related type of problem.

Which addition problem is the same as 525 + 379? Let's just break it down. So we have a 5 in the hundreds place, so that would be 500. And then we have a 3 in the hundreds place, so + 300. Then we have a 2 in the tens place, so it's two 10 or 20.

And then we have a 7 in the tens place, so that's + 70. And then last but not least, we have a 5 in the ones place, so that's just going to be 5. And then we have a 9 in the ones place, so that's just going to be equal to 9.

So which of these choices is the same as what I just wrote over here? 500 + 300. So this first choice has no 500 or 300, so we can rule that out. 500 + 300 + 20 + 70 + 5 + 9; that's exactly what I wrote down.

This last choice breaks down; they wrote 90 instead of 9. And then they wrote 5, and then they wrote 7 instead of 70. That 7 is in the tens place; it's not in the ones place, we ruled that one out as well.

More Articles

View All
Change in angular velocity when velocity doubles
We’re told that a car with wheel radius r moves at a linear velocity v, and this is a bolded v to show that it’s a vector. Suddenly, the car accelerates to velocity 2v. How does the angular velocity of the wheels change? So pause this video and see if you…
6 Millionaire Habits I Wish I Knew At 20
What’s up you guys, it’s Graham here. So I know a lot of people say your 20s are the most transformative and influential years of your entire life, and I have to say it, but that is absolutely a load of truth. Because looking back over my last 10 years, I…
Templating a contract with variables | Intro to CS - Python | Khan Academy
Let’s work together on a program that uses variables and user input. Here’s the problem I’m trying to solve: my friend Deshawn has a catering business, and for each catering job that he takes, he needs to write up a contract between him and the client. Ev…
How To Beat The Odds When Buying Stocks (Mohnish Pabrai: The Dhandho Investor)
[Music] So there’s been a lot of people trying to get into the stock market over the past year or so, and I actually just finished re-reading Monish Pabrai’s book, “The Dondo Investor,” which is a very good stock market book. But I’ve actually forgotten h…
Alligator Moms Are Nature's Helicopter Parents | National Geographic
[music playing] NARRATOR: What would you do if you could not chew? Did Dr. Seuss write this script or maybe Roald Dahl? [singing] What would you do if you could not chew? Simple. You just thrash your food apart. Alligators go through 2,000 to 3,000 tee…
The Cookiecutter Shark | Sharks of Bermuda Triangle
NARRATOR: The Bermuda Triangle contains some of the deepest trenches in the world. The Puerto Rico Trench at the Triangle’s southern point reaches depths of over 27,000 feet. But Dr. Gallagher suspects that Mabel may frequent the Tongue of the Ocean, a st…