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Here's a "trick":
When multiplying two two-digit numbers "ab" and "cd" (where "a" and "c" are the tens digits and "b" and "d" are the ones digits of the respective two-digit numbers):
Step 1: Add the products of a*d and b*c and multiply by 10 (i.e., add a zero to the end of that)
Step 2: Multiply b*d and add that to the result in Step 1.
Step 3: Multiply a*c*100 and add that to the result in Step 2.
Example: 8 is "a", 3 is "b", 4 is "c", 2 is "d"
83
x42
Step 1: (8*2+3*4)*10 = 280
Step 2: 3*2 + 280 = 286
Step 3: 8*4*100 = 3200; 3200+286=3486 <-- Final Answer
Basically multiply the diagonals, add them together, multiply the columns add to previous results. A lot of the time, I find it easier to do this in my head since there are less numbers to keep track of. My friend's dad figured this out (by himself!) and taught us when we were in elementary school. There's probably a similar method for three digit numbers. If anyone figures it out, please enlighten us!
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