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
These Two Young Bushmen Hope for a New Life in the Modern World | Short Film Showcase
[Music] Love h h h h my oh my. [Music] Fo I [Music] [Music] note foree. [Music] Spee [Music] when I go through new, I see a lot of hopeless faces. People who are here, we are undergoing a lot of change, and we are losing our way of life. Foree [Music] if …
How To See Air Currents
If there were a portal through which you could see all of the invisible air currents, temperature gradients, and differences in pressure and composition of air, then this is what it would look like to strike a match. This is helium being squeezed out of a…
Intermediate value theorem | Existence theorems | AP Calculus AB | Khan Academy
What we’re going to cover in this video is the Intermediate Value Theorem, which despite some of this mathy language, you’ll see is one of the more intuitive theorems, possibly the most intuitive theorem you will come across in a lot of your mathematical …
Bullet vs Prince Rupert's Drop at 150,000 fps - Smarter Every Day 165
All right, Keith. Prince Rupert’s drop. Prince Rupert’s drop, right? Paper submitted from 1660 to the Royal Society. So this is a very early stuff. Hey, it’s me, D. Welcome back to Smarter Every Day. I am in the basement of the Royal Society in London, En…
Expectation vs Reality: How to be a YouTuber For Beginners (2019)
What’s up you guys? It’s Graham here, so let’s talk for a minute, figuratively speaking, of course, because we actually have to make this video over 10 minutes long to be able to place mid-roll ads in the video about what it’s like to be a YouTuber. Is it…
Dario Amodei: Anthropic CEO on Claude, AGI & the Future of AI & Humanity | Lex Fridman Podcast #452
If you extrapolate the curves that we’ve had so far, right? If you say, well, I don’t know, we’re starting to get to like PhD level and last year we were at undergraduate level, and the year before we were at like the level of a high school student. Again…