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Foreheadson
First I tried to do ugly multiplications. after 5 minutes, I realized that whatever I was doing was not thr Gmat way. than I looked at thr answer choices. I tried x=1, to reduce the possible answer choices.
first i simplified. 0.000125 is an ugly number, so I used approximation to 0.0001. bcs sqrt is easy, it's 0.01. 0.015*(0.5sqrt(x)-0.5)=0.01. if x=1 the answer is 0. it must be higher. leaves with D and E.
tried x=4. 0.015*(0.5*2-0.5)=0.015*0.5=0.0075. less than the actual answer of 0.01. so answer is clearly E.
this way I did the task in 2 mins. Hope it helps.

Posted from my mobile device


That's a good way for this question. I solved it by equating the number of digits count - before & after the decimal - for LHS & RHS. This helped me solve it in 15 seconds (after wasting 3 minutes in complete calculation).
I acknowledge, your way is better as it is more general and error proof.
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Took me 15 seconds to solve.

(\sqrt{0.000125}+0.005)(\sqrt{0.25x}−0.5)=0.01

Let's approximate the number for digits.
=> \sqrt{0.000125} = a (say) has 3 digits after decimal
=> (\sqrt{0.000125}+0.005) = a + 0.005 again will have 3 digits after decimal.
=> Therefore, for LHS in given expression to be equal to RHS, ie 0.01, (\sqrt{0.25x}−0.5) should have 1 to 2 digits before decimal.
=> x must have at least 1 digit before decimal. E is the only answer that satisfies this condition.

Therefore, E is the Correct Answer

**took me 15 seconds but after wasting 3 minutes on manual calculations. LoL!
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