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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well i did it differently,
i checked the answers and i squared the first and divided it by 2.3 and fount out that it's the closest to 10^9, all the other are just way off
though i guess it may not work as well

If we have a problem 10^4, is not the solution 100,000? Since the decimal point is in the end of 10. so we carry the point 4 step right.
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47958



Answer - A