Numeracy spill in aisle 3
Someone hand the international desk at the Associated Press a calculator, please.
This story appeared in my local paper:
HARARE, ZIMBABWE -- The government announced a nearly 700 percent increase in the price of corn, the mainstay of the Zimbabwean diet ...
The price of an 11-pound bag of cornmeal -- which provides an average family of six one meal a day for about five days -- now will sell for $1.45 up from 21 cents.
Math alert (no reason to be scared)
The "percent increase" is one less than the "percent of." And the "percent of" is the simple ratio. So, yes, $1.45 is
The formula is simple ((ending number/starting number) -1) x 100 = percentage difference. (If it's negative, it's a percentage decrease, positive is a percentage increase.)
Let's do it the elbow grease way:
42 is double 21, but a 100 percent increase (21+(1 x 21))
63 is triple 21, but a 200 percent increase (21 + (2 x 21))
84 is quadruple 21 but a 300 percent increase (21 + (3 x 21))
105 is quituple 21 but a 400 percent increase (21 + (4 x 21))
126 is sextuple 21 but a 500 percent increase (21 + (5 x 21))
147 is septuple 21 but a 600 percent increase (21 + (6 x 21))
Since 145 falls between those last two, it cannot be any greater than a 600 percent increase from 21. Certainly, a
(The same percentage works out --and the AP is just as wrong -- when the amounts are in Zimbabwe dollars.)
* Note: I have changed the figures earlier to 590/690 to reflect the actual math in using $1.45 and 21 cents. However, there is some error due to conversion. The figures given in the AP story for Zimbabwe dollars work out to 583 percent, so that probably is more correct.