Expert: Lynn Houston - 11/22/2010

Question
I have a friend who did an equation 0.25 x 12.8 and got 32 as the product. so i am trying to explain to her using number sense rather than rules, that this computation is not reasonable and I have been trying to give her suggestions on how to do this equation correctly.
However, she is not understanding me...could you please help. Thank you

Answer
Ok, I can think of two things you might try.  One is logic.  .25 = 1/4, so by multiplying something by 1/4, you're dividing it by 4.  12.8 divided by 4 cannot be 32.

The other, is to change both decimals into fractions and then multiply, so you have 1/4 (12 4/5).  12 4/5 = 64/5 so
1/4(64/5) = 64/20 = 3 4/20 = 3.2

Hope this helps.