This is a simple "trick", but still handy, especially if you're just beginning training for competitions like chapter MATHCOUNTS, the AMC 8, etc.

Suppose you wanted to find 49% of 190. At many schools, they would teach you to move the decimal point two places over in the 49% to get 0.49, and multiply it by 190, a tedious and annoying process (much like the awful time I spent today, doing 24 problems that involved finding the inverses of 3 x 3 matrices for my math homework without any calculators whatsoever, but I digress.)

But there's a faster way. A much faster way. First, note that if we find 40% of 190, and then 9% of 190, and add these two results together, we'll achieve our answer.

Now note that if we find 10% of 190, and multiply that by 4, we'll have 40% of 190. 10% of 190 is simply . Multiplying by 4 gives us 76. (And there are several ways you could have done that too! + or .)

Similarly, if we find 1% of 190, and multiply that by 9, we'll get 9% of 190. So, 1% is 1.9, and .

Thus, 49% of 190 is .