The publication of this column in Communications of the ACM provoked many interesting letters. One reader told of hearing an advertisement state that a salesperson had driven a new car 100,000 miles in one year, and then asking his son to examine the validity of the claim. Here's one quick answer: there are 2000 working hours per year (50 weeks times 40 hours per week), and a salesperson might average 50 miles per hour; that ignores time spent actually selling, but it does multiply to the claim. The statement is therefore at the outer limits of believability.
Everyday life presents us with many opportunities to hone our skills at quick calculations. For instance, how much money have you spent in the past year eating in restaurants? I was once horrified to hear a New Yorker quickly compute that he and his wife spend more money each month on taxicabs than they spend on rent. And for California readers (who may not know what a taxicab is), how long does it take to fill a swimming pool with a garden hose?
Several readers commented that quick calculations are appropriately taught at an early age. Roger Pinkham wrote
Several other readers discussed teaching this attitude to children, from the viewpoints of both parent and child. Popular questions for children were of the form ``How long would it take you to walk to Washington, D.C.?'' and ``How many leaves did we rake this year?'' Administered properly, such questions seem to encourage a life-long inquisitiveness in children, at the cost of bugging the heck out of the poor kids at the time.
Copyright © 1999 Lucent Technologies. All rights reserved. Mon 9 Aug 1999