Quote:
\(\frac{0.025 \times 7.5 \times 48}{5 \times 0.0024 \times \frac{3}{4}}=\)
(A) 0.1
(B) 0.2
(C) 100
(D) 200
(E) 1,000
Let's first convert \(\frac{3}{4}\) to \(0.75\), its decimal equivalent, to get: \(\frac{0.025 \times 7.5 \times 48}{5 \times 0.0024 \times 0.75}=\)
Key property: \(\frac{ABC}{DEF} = \frac{A}{D} \times \frac{B}{E} \times \frac{C}{F} \)Strategy: I'm going to use this property to split the original fraction into the product of 3 individual fractions.
There are a few different ways I can split up the fraction. For example, I could pair up 0.025 and 5 to get 0.025/5, but that seems like a pain to calculate.
Similarity, I could pair up 48 and 0.0024 to get 48/0.0024, but that also seems like a pain.
Instead, I'm going to use the fact that the answer choices are extremely spread apart in order to pair up values that I can easily approximate. So, we get: \(\frac{0.025}{0.0024} \times \frac{7.5}{0.75} \times \frac{48}{5}\)
Let's evaluate (or approximate) each fraction individually.
\(\frac{0.025}{0.0024} ≈ \frac{0.025}{0.0025} ≈ \frac{(1000)(0.025)}{(1000)(0.0025)} ≈ \frac{250}{25} ≈ 10\)
[multiplying numerator and denominator by 1000 resulted in a fraction with integer values only, which made it easier to calculate]\(\frac{7.5}{0.75} = \frac{(100)(7.5)}{(100)(0.75)} = \frac{750}{75} = 10\)
\(\frac{48}{5} ≈ \frac{50}{5} ≈ 10\)
Substitute values to get: \(\frac{0.025}{0.0024} \times \frac{7.5}{0.75} \times \frac{48}{5} ≈ 10 \times 10 \times 10 ≈ 1000\)
Answer: E
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Brent Hanneson – Creator of gmatprepnow.com
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