y = 1/2 - 1/3 + 1/6 - 1/10 + 1/12 - 1/14 + 1/16
The terms are arranged from the largest to smallest. The smaller terms are pretty negligible, so it suffices to only worry about the bigger terms.
So I would start with 1/2 - 1/3.
Hm, that's 1/6. Hey, the next term is 1/6 too, might as well include that since the math is easy.
So 1/6 + 1/6 = 1/3 = 0.33
Now let's have a look at the rest of the terms: - 1/10 + 1/12 - 1/14 + 1/16
-1/10 + 1/12 is something slightly negative.
-1/14 + 1/16 is something slightly negative.
So now we have 0.33 + something slightly negative, or something slightly under 0.33.
Looking at the answer choices, B fits the bill.
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