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Lesson 3: Multi-digit multiplication

# Estimating multi-digit multiplication

Learn the skill of estimating the product of multi-digit numbers. Watch a demonstration of the process. The video emphasizes the importance of estimation in simplifying complex multiplication problems.

## Want to join the conversation?

• 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)
• what is estimating
• estimating is rounding to get an approximate answer for example 279*23 estimated would be 300*20 = 6000
• i don't understand? this fifth grade multi-digit ):
• For estimating multi-digit multiplication we first round the numbers that are being Multiplied Ex: 482 × 32 -> 500 × 30. Although we rounded the numbers it's still a bit hard. We can solve this by breaking up 30 into 3 and 10. Now the equation looks like this 500 × 3 × 10. Now we can just multiply at this point. 500 × 3 = 1500 × 10 = 15,000.
• 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
• This is simple
• If this is simple then you should try something harder to challenge yourself. There is nothing wrong with learning extra!
• Thx for the vid it rlly helped []:
• the answer to this question is some math junk and stuff
• Roses are red
Violets are blue
Back in my day...