Question 745006
How do i solve 49 times 19... Mentally? 
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There are many ways for this one.
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= 19*7 then *7
= 19*50 then -19 the best for this one, imo
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Another method, not so attractive for this one is
Get the average = (49 + 19)/2 = 34
Diff between ave and numbers = 15
49*19 = avg^2 - diff^2 = 1156 - 225
This works well for a lot of them, not so good for this one.
eg, 37*39 = 1443 easily (if you know what 38^2 is)