Fast way of dividing 138/.82 ?

[robertpatrick]

I'm specifically referring to question # 5 in Problem Solving, OG 11.

Is there a way to do that long division in a short amount of time?? If so, I missed something about long division..

Anybody have any tips?

[VP_Tatiana]

These are the steps I go through to work out this problem in my head:

First, I see we can divide numerator and denominator by 2, so we have 69/.41.

I don't have access to the particular problem you referenced, but I am guessing that the answer choices are far enough apart that we can estimate. (If not, you'll have to do long division of 6900/41.) Now, we know that 69/.41 will be pretty close to 70/.4. Since 10/.4 = 100/4 = 25, 70/.4 = 7*25=175. (The actual answer is 168.29.)

Hope that helps,

Tatiana