The cunning Areas, December 98

Because it is Xmas time, I want to be cool with your brain cells! Here are 2 easy area finding problems:

1) Find the area of the grey-shaded parallelogram AKCL in the fig.1) below. Consider that: a) ABCD is a square with 3 cm side length; b) KD = 5 cm.

2) Now, find the area of the polygon in fig.2). Consider that: a) AB = AD = 3 cm; b) DC - BC = 1 cm.

You have to use the shortest way to resolve these problems, a formula with more than 2 terms (binomial) is not acceptable. Have I forgotten something? ah …MERRY CHRISTMAS and HAPPY NEW YEAR!!!

Print this page and try to solve these puzzles

©96-98, Sarcone & Waeber, Lausanne

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The solutions are:

a) 3(5-3) = 6 cm²;

b) (3 x 3) - 1/4 = 8 3/4 cm²;
the formula is: AB=AD=c; BC=a; DC=b; |a-b|=n;
(c - n/2)(c + n/2) = c² - (n/2)²

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