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Last Updated on January 10, 2022
GMAT OFFICIAL GUIDE PS
Solution:
We are given √(4.8 x 10^9), and we need to determine the answer choice that is closest in value. We first simplify the expression by eliminating the decimal point in 4.8. To do this, we can move the decimal one place to the right to get 48 and simultaneously reduce 10^9 to 10^8. So we need to estimate √(48 x 10^8). Notice that 48 is very close to 49, which is a perfect square. Note, too, that the square root of 10^8 is easy to calculate because the exponent is now an even number. So let’s evaluate √(49 x 10^8):
√(49 x 10^8)
√(49) x √(10^8)
7 x 10^4
70,000
Thus √(4.8 x 10^9) ≈ 70,000.
Answer: B
