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Estimating multi-digit multiplication

Estimate to find reasonable solutions to multi-digit multiplication problems.

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• what is estimating
• estimating is rounding to get an approximate answer for example 279*23 estimated would be 300*20 = 6000
• I have a question. So for the first problem, where we are trying to estimate (29)(3198) = 92742, (I may be wrong) but I think it actually is a closer approximation to the real value if we use a rounded value of (30)(3000)=90,000 (which is an underestimation of -2742 from the real value) than if we use (3200)(30) = 96,000 (which is an overestimation of +3258). Similarly, for the second problem, for trying to find (137)(18)=2466, if we round it to (130)(20)=2600, we get the closest approximation, which is +134 from the actual value. If we use (140)(20)=2800, it is an overestimation of +334, and if we use (137)(20)=2740, it is an overestimation of +274, and if we use (100)(20)=2000, it is underestimation of -446. What I'd like to know is how do we go about determining or having a rule for when the values are a closer approximation, while still being able to calculate the values quickly in your head or on paper?
• dude wrote an entire book page (not a insult a compliment)
• I have a question. So for the first problem, where we are trying to estimate (29)(3198) = 92742, (I may be wrong) but I think it actually is a closer approximation to the real value if we use a rounded value of (30)(3000)=90,000 (which is an underestimation of -2742 from the real value) than if we use (3200)(30) = 96,000 (which is an overestimation of +3258). Similarly, for the second problem, for trying to find (137)(18)=2466, if we round it to (130)(20)=2600, we get the closest approximation, which is +134 from the actual value. If we use (140)(20)=2800, it is an overestimation of +334, and if we use (137)(20)=2740, it is an overestimation of +274, and if we use (100)(20)=2000, it is underestimation of -446. What I'd like to know is how do we go about determining or having a rule for when the values are a closer approximation, while still being able to calculate the values quickly in your head or on paper?
• another book page
• I'm too afraid add 5 because I was wrong minus 4. But this isn’t much perfect. should be 4/4 not 3/4 I don’t want to.
• im a little confused you made it tooo hard to understand for me atleast can you do another one that is easyer to undeerstand please! thanks
• Hello! I'm confused by how you would go about estimating. Can anyone explain this to me? I struggle with math, especially multiplication. Any help would be highly appreciated!

• ok so heres a example: 10 15 20 the number is 15.45 so it above 14 to 10 so it is 20.