MathRevolution wrote:

Which of the following is the closest value of x such that \(x^{20}+x^2+0.0000019=0.09\)?

A. 0.1

B. 0.01

C. 0.3

D. 0.03

E. 0.003

When a GMAT question tells us to find the "closest value" or the "approximate value," this usually gives us the go ahead to estimate.

First recognize that, for all 5 answer choices, the value of x^20 becomes

inconsequentialFor example, if x = 0.1, then x^20 = (0.1)^20 = (1/10)^20 = 1/100000000000000000000

The same applies to all 5 answer choices.

Since the value of x^20 has almost no effect on the equation, we can safely ignore it.

Likewise, the value 0.0000019 is very very very small in relation to 0.09

So, we can safely ignore it.

So, our equation becomes x² ≈ 0.09

Solve to get: x ≈ 0.3

Answer:

Cheers,

Brent

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Brent Hanneson – GMATPrepNow.com

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