Burt Kaliski Jr. (@modulomathy)

4/7/12 11:55 AM

#math trivia for #April7: #98 is the product of a number and its double. What’s the number, and what product near 10000 has this property?

The number is 7: 7*14 = 98. Consider the equation 2x^2 = 98.

The product near 10000 with this property is 71*142 = 10082. This is related to sqrt(2)/2, which is approximately .707. Rounded to the nearest integer, 10*sqrt(2)/2 is 7, and 100*sqrt(2)/2 is 71. The relevant equation for 71 is 2x^2 ~= 10000, or x^2 ~= 5000 = 100^2/2.

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