plz i need help. i think barron's math2 contains some error?

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<p>Hello, I was working on exponential and logarithmic functions on barron's math2. When I finished exercises on page 95 and checked my answers, I got some problem.</p>

<p>Page 95, Barron's SAT subject test math level 2
question7: If log b (xy) < 0, which of the following must be true?
I thought the answer should be (D) xy > 0, because only when xy>0 the function makes sense. But the answer was (E) none of the above ("since no restriction was put on b"). Am I wrong, or is Barron's wrong?</p>

<p>question 10: If $300 is invested at 3%, compounded continuously, how long (to the nearest year) will it take for the money to double? (If P is the amount invested, the formula for the amount, A, that is available after t years is A=Pe^(0.03t).)
I got the answer t=23.1, but I think this year must be complete in order to get the money double. So I choose (C) 24 years. But the answer said (D) 23 years. But after 23 years there would only be $598, not exactly $600 or more than $600. Could you please explain this to me?</p>

<p>Thank you so much I'm taking the test on June 4.</p>

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<p>If log_b (xy) < 0, then xy < b. Sure, it would only be defined if xy > 0, but if xy was equal to, say, b^2, you wouldn’t get a negative number out of it. If xy < b wasn’t one of the choices, then the answer should be (E).</p>

<p>They say to the nearest year, so I guess they want you to round normally… Barron’s and other books can have problems which are iffy in that sense, but I’ve never seen anything like that in an actual test. If they gave any kind of question like that on the real thing the answer choices wouldn’t be nearly so bunched together.</p>

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<p>thank you so much…</p>