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# Estimating 2-digit multiplication

CCSS.Math:

## Video transcript

so we are asked question mark is roughly equal to this squiggly equal sign right over here this means roughly equal to so not exactly equal to 44 times 78 so one way to think about it is 44 times 78 is roughly equal to what so they're really asking us to estimate so I encourage you pause this video and try to think through how you would estimate what 44 times 78 is once again you don't have to get it exactly you just want to get it roughly and think about which of these choices are closer are closest to that estimation of yours all right now let's work through it together so for me the best way to estimate is to think about hey can I think of these numbers can i estimate these numbers or think about what are they roughly equal to and when I think about what they're roughly equal to I want to think about numbers that are easy to multiply potentially in my head so for example 44 is reasonably close to 40 so I could say that hey this is approximately equal to or roughly equal to 40 so that's my estimate of 44 or it's 44 is roughly 40 and then 78 I could say hey that's pretty close to 80 and so I could say this is roughly equal to 40 times 80 and this is pretty straightforward some of you might already recognize that 4 times 8 is 32 and then we have 4 tens and then we have 8 10 so it'd be 4 times 8 times 10 twice but if what I just said is confusing to you we could think about it this way 40 times 80 is the same thing as 4 times 10 that's 40 times 8 times 10 that's 80 and this is equal to I'm just going to switch the order here of this multiplication which we can do this is equal to 4 times 8 times 10 times 10 4 times 8 is 32 10 times 10 is 100 so we could say that this is equal to 32 hundreds or we could view that as 3,200 which you could also view as 32 hundreds and so that is this choice right over here now this isn't exactly what 44 times 78 is but it's roughly and this is useful sometimes in life you just have to get a rough sense of what something is going to be sometimes when you even are trying to find this exact product you just want your brain wants to check does that make sense let's say you went through some process to figure out this and you got and you you got some number that is you know close to close to 20 and you're like wait wait no but roughly when I think about 40 times 80 this should be close to 3200 I must have done something wrong so it also helps you keep a check on yourself