If K is the sum of the reciprocals of the consecutive integers from 43 to 48, inclusive, then K is closest in value to which of the following?
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This one had me stuck for a minute. I started adding them up directly and got lost in the fractions. Then I realized you can use the fact that all six numbers are around 45, so the sum is roughly 6/45 = 2/15. But 2/15 is about 0.133, and 1/8 is 0.125, so that's closest. Is that the right way to think about it?
Yeah, that's a good approach. The actual sum is a bit less than 6/45 because the reciprocals of the larger numbers pull it down a bit, but it's still closest to 1/8.
I did the same but then checked with the first and last terms: 1/43 ≈ 0.0233 and 1/48 ≈ 0.0208, average ≈ 0.022, times 6 ≈ 0.132. Still points to 1/8.
I got 1/8 but I wasn't sure if I should pick the closest. The exact sum is about 0.132, and 1/8 is 0.125, 1/6 is about 0.166, so 1/8 is closer. But is there a faster way without calculating?
You can bound it: the sum is between 6/48 = 1/8 and 6/43 ≈ 0.1395. Since 0.1395 is closer to 0.125 than to 0.166, it's 1/8. But you still need to check.
I thought this was a bit tricky because the answer choices are 1/12, 1/10, 1/8, 1/6, 1/4. I initially guessed 1/6 because 6/45 = 2/15 ≈ 0.133, and 1/6 is 0.166, but 1/8 is 0.125. So 1/8 is closer. Good reminder to always compare decimals.
Nice question! I like how it forces you to estimate rather than compute exactly. The key is recognizing that the sum is approximately 6 divided by the average of the numbers, which is about 45.5.
What it tests
Your fluency with the order of operations, fractions, decimals, and basic number sense — the foundation every quant question leans on.
Common trap
Applying the order of operations out of sequence or rounding intermediate values before the final step.