How would you calculate a percent increase in your head?

[danthaman]

Hey guys,

I am preparing for an interview tomorrow, and there will be simple math problems. The catch is that we have to do it in our head. Could someone give me their thought process as to how they would, step-by-step, solve the following problem:

10.6/1.10 = X.

I have done complex math in my life, but cannot figure out how to do this in my head. Funny.

Thanks,

D.

 

[mmm4444bot]

This is how I just reasoned mentally, but I'm relaxed, sitting in a quiet room, without a care in the world. (Your mileage might vary.)

10.6 divided by 1.1

That's the same as 106/11

10 times 11 is 110

106 is less than 110, so the answer must be smaller than 10

9 times 11 is 99 (that's too small)

The answer is somewhere between 9 and 10

99 to 106 to 110

The difference in position of 106 between 99 and 110 is 7 on one side of 106 and 4 on the other

The answer must be more than halfway between 9 and 10

It feels like 10.6/1.1 must be around 9.7 (give or take) ?