implicity

I was trying to do 97 times 5 in calculator. But I quit. Instead I subtracted the answer of 3 times 5 from 100 times 5. Probably many people do the same thing.
 

by trying to do a calculation yourself, you learn these tricks which make it much much easier.

i can add much faster than a calculator and probably multiply short numbers at similar speed.
 

How on earth did you calculate that? Did you do time tests against a calculator? Was there an impartial adjudicator?
 

are you challenging me?
 

Yes. You're on. Tomorrow?
 

tomorrow. i'll bring my calculator(s).
 

No, I think we should use a calculator belonging to someone impartial. Gwen? Liz?
 

this is the other disadvantage of calculators; they can't be trusted.
 

One of the reasons I hate some scientists:

Several months ago, I was at lunch with some friends from work. There seemed to be some confusion in figuring out how much to tip the waitress. I trotted out the old trick of calculating 15% by moving the decimal place of the bill over by one place and adding that value to half of that value to find fifteen percent. I noted that I usually tip 20% or better, which is even easier to calculate. My friends stared at me like I was retarded and asked, "are you sure?" in a really sarcastic way. Obviously, they were already familiar with this method of mental arithmetic. However, every goddamned time we go out for lunch, there's a bunch of, "Hmmm ... let's see ... uh ..." when trying to figure out a 'starting value' for the tip, from which we might factor in quality of service, etc. to determine the end value.

They are perfectly familiar with a quick method of doing the arithmetic, yet seem determined not to use it. I swear, I'm going to buy one of those stupid tip calculators and start carrying it around with me.