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

Multiplying by tens word problem | Math | 3rd grade | Khan Academy


2m read
·Nov 11, 2024

A volunteer group is planting trees at five different parks. They planted 90 trees at each park. How many trees did the group plant in all?

So here's what we know: we know that this group went to five different parks, very kind of them, and planted 90 trees at each of those parks. So if we want to know the total amount, we could do a couple of things. We could say they planted 90 trees at Park 1, plus 90 more at Park 2, plus—you see where this is going—90 more at Park 3, plus 90 more at Park 4, and finally, 90 more at Park 5.

One way to solve this would be to add all of those 90s. We could do it; it'll take a while, but we could get there. Or we could say that the group planted 90 trees five times. Five times they planted 90 trees, so 90 * 5.

Let's solve both of these! Either are great ways to get to our solution, but maybe solving both of them will help us see if we liked one way better, if one felt simpler for us.

So, 90—the number 90—we can think of as 9T. I'll write that up there, and that'll help us add.

9T + 9T is 18T, plus 9 more tens is 27T, plus 9 more tens is 36T, and the last nine tens gets us 45T, or 450. That zero is because we're talking about tens. So, the group planted 450 trees.

Now, let's try the multiplication way and see how that goes. So again, 90 we can think of as 9T times 5. So if you have 9 tens five times, you have 45T. And 45T is again 450; get that zero on the end.

Both ways we see this is a very generous group; they planted 450 trees. Either way, we could add or we could multiply. For me, the multiplication gets me there faster. I like the multiplication way, but either way, we can see 90 trees at five parks is 450 total trees.

More Articles

View All
Transitioning from counting to multiplying to find area | 3rd grade | Khan Academy
This square is one square unit. So, what is the area of rectangle A? The first thing we’re told is that each of these little squares equals one square unit, and then we’re asked to find the area of rectangle A. Here’s rectangle A, and area is the space th…
Re: Leap Years, 2012 & The Mayan Calendar
Hello, Internet. A lot of you sent me this image making the rounds which concerns the Mayan prediction that the world will end on December 21, 2012. The claim is that the Mayan calendar short counted the years because they forgot about leap days, so the w…
Collecting Crab Pots | Alaska: The Next Generation
You’ll learn as you’re going and get older, you make your own shortcut. You’ll always make it back home. Ready, Glyn? Oh, yeah. Glyn and I are off to pull out crab pots from Olga Bay, where he has one and I have one. And that increases our chances of get…
Sonic Postcards from The Appian Way | Podcast | Overheard at National Geographic
That was our first experience with an unpassable section of the Appian Way. We were with Ricardo at that point. Ricardo told us the path is not clear, so probably we have to cross the river. But let’s see. Writer Nina Strolik and photographer Andrea Fraz…
Diving With Bullsharks | World's Biggest Bullshark
Neil and James search a shipwreck for the mega shark, Big Bull, and other large bull sharks that may be her descendants. “I’m good over here,” Neil says. Bull sharks have a pack-like mentality and swarm around possible food. They surround the divers. Ne…
Crowd-funding: Tips
So, as some of you might know already, uh, I’ve been running a crowdfunding campaign to fund the production of the follow-up to my George or to help animation that I made last year. It’s in the final days of the campaign, so if you didn’t check it out alr…