Teachers and parents! If your students are struggling with long division, this Big 7 division strategy can help! I’ve also heard this method called “Lucky 7” but this alternative division method can help divide big numbers, decimals, and division with remainders!
I give you 2 examples using this Big 7 strategy. This is a great strategy for 3rd 4th or 5th grade! I work with students all the time who struggle with dividing using the standard algorithm. This is a great way to help students build confidence in themselves when doing long division and provide that stepping stone to eventually use the standard algorithm!
Transcript
0:00
Hi, my name is Beth from My Tutoring Bee, and today we are going to redo one of the videos I made 10 years ago—one of my very first videos on YouTube. It’s all about Big Seven Division. So, let’s get started!
0:22
I’m celebrating 10 years on YouTube, and this is still one of my most popular videos. It’s all about Big Seven Division, which is an alternative method to the standard algorithm for long division. I’ve got a couple of problems here that we’re going to go through, and I’ll show you how this works.
0:38
To start off, we’ve got 329 ÷ 7. This looks like what you’d typically see in a long division problem. However, to make it a Big Seven problem—and I’ve heard this method called different things—the one I hear most commonly is “Big Seven.” When we put this line going all the way down the side here, this bracket now looks like a big seven, which is where the name comes from.
1:00
Now, what we’re going to do is think about how to take away groups of seven from 329. We could just subtract seven and keep doing that over and over again, counting how many times we subtract seven. However, that could take a while, so we’re going to find larger groups of seven that we can subtract from 329, making it easier and quicker to count.
1:27
One of the reasons this method works so well is because you don’t have to be exact with the multiples of seven. We’ll start off with some big groups of seven and subtract those to get the number down to a smaller, more manageable one. Then we’ll see how many times seven can go into 329.
1:43
Let’s start with 10. I’ll write “10” over here on the side to keep track of how many groups of seven we’re subtracting. I know that 7 × 10 is 70, so I’m choosing 10 because it’s an easy multiple to work with. I’ll subtract 70 and see where that gets us, and then we can adjust from there.
2:25
When we subtract, we get 259. That’s still a pretty big number, so I’m going to see if I can go a little higher and subtract more groups of seven. This time, let’s take out 20. Again, I’m choosing numbers that are easy to multiply. 2 × 7 is 14, plus the zero at the end gives us 140.
2:58
Now, let’s subtract 140. This will get us down to a smaller number more quickly. After subtracting, we get 119.
3:11
Now, I’m going to go back to subtracting 10 groups of seven, which gives us 70. So, we subtract 70 from 119, and we’re left with 49.
4:01
At this point, I know that 49 is a multiple of seven. However, if you don’t know that, that’s okay. You can continue subtracting groups of seven using numbers that you do know.
4:11
Let’s say I don’t know that 49 is a multiple of seven, but I do know what 5 × 7 is. So, I’ll subtract five groups of seven. 5 × 7 is 35. Subtracting 35 from 49 leaves us with 14.
4:35
Now, I know that 7 × 2 is 14, so I’ll subtract two groups of seven. This gets us down to zero, and we’re done with the problem.
4:49
Now, how many groups of seven did we subtract? Let’s add them up: 10 + 20 + 10 gives us 40, and then 5 + 2 gives us 7. So, we subtracted 47 groups of seven.
5:07
I have another example for you. This time, I want to show you how this method can be helpful when dividing larger numbers or when dividing by a two- or three-digit number. Sometimes, you might not know your multiples of 15 as well as you know single-digit multiples. That’s where this method really shines.
5:33
Let’s go ahead and draw the line down the side again and start taking out groups of 15. Let’s start with 100. I don’t know—it just feels like a good starting point. You can start with whatever amount of groups of 15 you want, as long as it doesn’t go over the number you’re dividing.
5:55
1 × 15 is 15, and then we add the two zeros at the end, so we’re subtracting 1,500.
6:08
When we subtract, we’re left with 814. This is still a big number, so I want to subtract more groups of 15. Let’s go with 200 this time. 2 × 15 is 30, plus the two zeros gives us 3,000.
6:28
Subtracting 3,000 leaves us with 514.
7:05
Next, let’s go with 300 groups of 15. 3 × 15 is 45, plus the two zeros at the end gives us 4,500.
7:13
When we subtract, we’re left with 14.
7:19
Now, I can subtract one group of 15. 14 – 15 gives us 4, which is smaller than our divisor. So, we have a remainder of 4.
7:43
Now, let’s add up how many full groups of 15 we subtracted. From our hundreds, we have 100 + 200 + 300, which gives us 600. Then, we have 30 from the tens, and 4 from the ones. So, we have a total of 634 with a remainder of 4.
9:47
That’s how you do Big Seven Division. Please let me know in the comments what you think! Have you tried this method before? Have you heard of it? I’d love to hear your thoughts. I’d also love it if you let me know any particular skills you’d like me to make videos on.
10:00
And last but not least, please like and subscribe. That really helps me to continue making these videos for you. I’ll see you next time!
How to do Big 7 Division Strategy (2014)
It’s my 10 year YouTube Anniversary! So to celebrate, I’m reviewing some of my first videos I ever made back in 2014! This one is all about “Big 7” Division. This was my second video I posted on YouTube and still one of my most popular videos even today.
Extra Credit
If you are looking for other math YouTube videos that pair well with this skill, try these:
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