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Kate G.
Tutor for 4 years
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SAT II Mathematics Level 2
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Question:

What is the distance in space between the points with coordinates $$(-3, 6, 7)$$ and $$(2,-1,4)$$?

Kate G.

We can use the Euclidian distance formula of $$d=\sqrt{(x_2-x_1)^2 + (y_2-y_1)^2 + (z_2-z_1)^2)}$$ to calculate this distance. We plug in to get $$d=\sqrt{(2-(-3))^2+(-1-6)^2+(4-7)^2}$$ and simplify to get $$d=\sqrt{(5)^2+(-7)^2+(-3)^2} = \sqrt{25+49+9} = \sqrt{83}$$. So the distance between these two points is $$\sqrt{83} \approx 9.11$$.

SAT II Biology E/M
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Question:

Example question from CollegeBoard's website: Nitrogenous base that occurs in RNA but not in DNA? A) Deoxyribose B) Ribose C) Uracil D) Cytosine E) Thymine

Kate G.

Deoxyribose and ribose are not nitrogenous bases. While they do occur in DNA and RNA (respectively) they are the sugar backbones and not the bases that the question is referring to, so we can eliminate options A and B. Of choices C, D, and E, all three are nitrogenous bases. However, both cytosine and thymine occur in DNA. Uracil, on the other hand, is only found in RNA. (Side note: thymine is only found in DNA - wherever thymine occurs in DNA, it is replaced with uracil in the RNA copy). From this we can conclude that the answer is (C) Uracil.

Biology
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Question:

Why is it not correct to say that individuals in a population have adapted to their environment?

Kate G.

When used in the context of evolution, adaptation refers to the changes a population undergoes due to natural selection. Just as I could not change my skin color to better protect me from sunlight if I move near the equator, individuals cannot adapt to their environments. (However, they can acclimate - such as learning to deal with the heat). Natural selection selects for those organisms that are best suited for their environment (such as those with darker skin to protect from the sun), causing the population as a whole to adapt to be better suited the environment.

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