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

Estimating subtracting decimals


3m read
·Nov 11, 2024

  • [Instructor] Alright, now let's get some practice estimating, subtracting decimals. So, over here it says 12.93 minus 6.1 is approximately equal to what? This squiggly-looking equal sign you can view as roughly equal to or approximately equal to. So, pause this video and see if you can figure it out. And, you shouldn't really need paper for it. The whole point of estimation is to be able to do it quickly and get close to the answer. You don't have to get the exact answer.

Well, let's think about it. The way my brain would do it is 12.93-- Let's just round each of them to the nearest whole number. So, this is going to be approximately 12.93 if I round to the nearest one or to the nearest whole number, I'm gonna round up to 13. And 6.1, if I round to the nearest whole number, I'm gonna round down to six. So, I could say this is roughly 13 minus six which is equal to seven, and that is indeed one of the choices there.

And, when you're doing estimation, you might have gotten a slightly different result, but I'm guessing that the way that this question was set up, that if you do any type of reasonable estimate, that you're going to have a number that is closer to seven than any of the other choices. And to be clear, sometimes you could do this in your head. For example, 12.93 minus 6.1, you could say 12 minus six is going to be six.

And then you have 93 hundredths minus, you could do this as 10 hundredths. So, it's gonna be 93 hundredths minus 10 hundredths is 83 hundredths, plus .83. So, just like that, you could do something like this and say, alright, the answer here is gonna be 6.83 exactly. And that, once again, is approximately equal to seven.

But, the whole point of this exercise is to get comfortable estimating things because a lot of times in life you don't need the exact answer. You just need a rough answer, just to know the ball park of what you're talking about.

Let's do another example. So here, we are asked what is 56.75 minus 46.9 approximately equal to? Once again, pause this video and try to work it out. Well, here I'm gonna do the same thing. I'm just gonna round each to the nearest whole number and then subtract. And, I'm gonna write it out, but you could do this in your head.

So 56.75 rounded to the nearest whole number is 57 round up, minus 46.9, I would also round up to 47. And, in our head this is pretty straightforward. This is going to be equal to ten. And, that is indeed one of the choices. And, normally in life when you're estimating, you don't have choices like this. I guess this is just the easiest way for-- This if off of the Khan Academy exercises.

So, for someone to be able to grade it because estimations can be different, so you have to pick the one that's at least closest to what you came up as your estimate. Now, let's do one more example. And, I will write in purple. Alright. So, pause the video again. See if you can figure this out.

Alright, so 49.7, I'm gonna round up to 50, 4.16 I'm gonna round down to four. So, that's going to be approximately equal to 30-- Oh sorry, that's gonna be approximately equal to 46. And, we do indeed see 46 as one of the choices right over there.

So, hopefully you feel comfortable. There's nothing fancy going on here. The whole point of this is to just get comfortable doing things like this in your head and estimating and rounding numbers so you can get a ball park sense of what this difference is going to be.

More Articles

View All
My Tenant Horror Story.
What’s up you guys, it’s Graham here. So chances are, if you ask any real estate investor about their experience as a landlord, it’s pretty much inevitable that a large percentage of them will open up and tell you about at least one of their tenant horro…
Is Our Food Becoming Less Nutritious?
Is our food becoming less nutritious? Many people claim that the nutrient content in our food has been decreasing over the decades. But is this really true, and should we be worried? A study published in 2004 looked at 43 different common garden crops, a…
Long run supply curve in constant cost perfectly competitive markets | Microeconomics | Khan Academy
[Man] Alright, now let’s dig a little bit more into analyzing perfectly competitive markets, and in particular, we’re gonna focus on the long run. Remember, the long run is the time span where firms can enter and exit the market. Or, another way to think …
Biases in algorithms | Intro to CS - Python | Khan Academy
Algorithms increasingly control many areas of our everyday lives, from loan applications to dating apps to hospital waiting lists. As responsible consumers and now creators of algorithms, we need to think critically about how the success of an algorithm g…
5 Things to Know About Virunga | Explorer
[Music] Veranga is Africa’s oldest and largest national park. It’s an enormous area, 3,000 square miles of protected space. But perhaps most importantly, it’s home to most of the world’s critically endangered mountain gorilla. Barunga is a UNESCO World He…
Limits from graphs | Limits and continuity | AP Calculus AB | Khan Academy
So we have the graph of y equals f of x right over here, and we want to figure out three different limits. And like always, pause this video and see if you can figure it out on your own before we do it together. All right, now first, let’s think about wh…