How do you check the answer of a large multiplication like 8216*4215=36430440 without actually doing the multiplication.
Sum 8+2+1+6=17. Take modulo 9 = 8.
Sum 4+2+1+5=12. Take modulo 9 = 3.
Sum 3+6+4+3+4+4=24. Take modulo 9 = 6.
Now check 8*3=24 and 2+4 = 6.
Tuesday, January 02, 2007
Casting Out Nines
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2 comments:
This means that if u have a no like
36421440...
According to ur calculation it will come out as the rt result...?
certainly not :) !! i guess this is a necessary condition not a sufficient one. we can use this for a fast random check only to see if this is not satisfied
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