Explanation Always scan the answer choices
BEFORE performing any calculations.
Since the answer choice are very spread apart, we can be very aggressive with our estimation.
We're going to use a nice rule that says
√(ab) = (√a)(√b)We have √(2.3 x 10⁹)
Since 2.3 isn't an easy number to find the square root of, the above
rule doesn't help us much.
However, what if we do the following:
√(2.3 x 10⁹) = √(2.3 x 10¹ x 10⁸)
= √(23 x 10⁸)
How does this help?
Well, 23 is pretty close to 25 and we know that √25 = 5.
Can we do this? You bet. Remember that since the answer choice are very spread apart, we can be very aggressive with our estimation
We get:
√(23 x 10⁸) = (√23)(√10⁸)
≈ 5(10⁴)
≈ 5(10,000)
≈ 50,000
Answer: A
Cheers,
Brent
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Brent Hanneson - founder of Greenlight Test Prep