Tuesday, January 17, 2012

this week's Math Beast Challenge

From here:



Go to it! My answer will eventually appear in the comments.


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1 comment:

Kevin Kim said...

This one seems pretty straightforward. We're given that

[(x - 5)(x + 2)]/[(x + 5)(x - 2)] = 1

Multiply the equation by the denominator, and we get

(x - 5)(x + 2) = (x + 5)(x - 2)

Use FOIL to multiply each side out, and we see that

x^2 - 3x - 10 = x^2 + 3x - 10

Subtract (x^2) and add 10 to both sides, and we're left with

-3x = 3x

for which only one solution is possible:

x = 0

Since x = 0,

Quantity A is 5
Quantity B is 4

...so the answer is (A).