What is the value of: 1/3[(1/2 - 1/5)+(1/3-1/6)+(1/4-1/7)+...] ?

Question

What is the value of:  \frac{1}{3}  , where both denominators in successive terms increased by 1?

(A)  \frac{11}{19}

(B)  \frac{13}{36}

(C)  \frac{29}{49}

(D)  \frac{31}{43}

(E)  \frac{49}{59}

Anamika1496 · Answer

Answer B

Explanation below

Ankur17000 · Answer

The denominator has to be divisible by 3. Only B can be the answer.

lavanya.18 · Answer

Is there any other way to solve this question?

Imrane12 · Answer

Here is how I found the answer, hope other members will tell me if I make sense:

Calculating 1/2 - 1/5 and the following fractions all give denominators that are even numbers, can't find a logical link between the pacing of their denominators but for sure we can see they are even numbers so adding them will give an even number in the parenthesis.

Well, Even x odd = Even, example: 2 x 3 = 6.

1/3 will multiply the whole parenthesis, the denominator being 3 (odd), so without much calculation needed again i know that for sure the denominator of the result has to be even. Only B gives us an even denominator, the rest are all odd numbers so it doesn't make sense, so here is the answer.

Answer B.

What is the value of: 1/3[(1/2 - 1/5)+(1/3-1/6)+(1/4-1/7)+...] ?

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What is the value of: 1/3[(1/2 - 1/5)+(1/3-1/6)+(1/4-1/7)+...] ?

Prep Toolkit

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More than Quant/Verbal Abilities: Speed vs. Accuracy

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From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards