Answer:
21,504
Explanation:
This is the usual method multiplication is done "by hand."
6 × 3584 = 6 × (3000 +500 +80 +4)
= 6×3000 +6×500 +6×80 +6×4
= 18000 +3000 +480 +24
= 21000 +504
= 21,504
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Many of us are taught in grade school to do the multiplication right to left:
= 6×4 +6×80 +6×500 +6×3000
... writing down the digit corresponding to the place value of the product, and "carrying" any more significant digits to add to the next product.
Here, that looks like 6×4 = 24, write down 4, carry 2. 6×8 = 48, add 2 to get 50, write down 0, carry 5. 6×5 = 30, add 5 to get 35, write down 5, carry 3. 6×3 = 18, add 3 to get 21, write down 21. Then the product is 21504.
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When doing mental calculation, or using an abacus or soroban, it often works better to do the multiplication left to right, as shown in the answer above.