Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

What people who reach the high 700's do differently? We're going to share insights, tips and strategies from data we collected on over 50,000 students who used examPAL.

Re: Which of the following fractions can be written as the difference of r
[#permalink]

Show Tags

11 Nov 2016, 13:44

3

Top Contributor

1

stonecold wrote:

Which of the following fractions can be written as the difference of reciprocals of two consecutive integers?

A. 1/100 B. 1/121 C. 1/45 D. 1/56 E. 3/72

Great question!

First, let x and x+1 be two consecutive integers. So, 1/x and 1/(x+1) are the reciprocals. So, their difference = 1/x - 1/(x+1) To subtract these fractions we must find common denominators. So, 1/x - 1/(x+1) = (x+1)/(x)(x+1) - x/(x+1)(x) = 1/(x)(x+1)

Notice that the denominator is the product of two consecutive integers AND the numerator is 1 Check the denominators of the answer choices: A. 1/100 We can't write 100 as the product of two consecutive integers. ELIMINATE. B. 1/121 We can't write 121 as the product of two consecutive integers. ELIMINATE. C. 1/45 We can't write 45 as the product of two consecutive integers. ELIMINATE. D. 1/56 We CAN write 56 as the product of two consecutive integers (7x8). KEEP E. 3/72 We CAN write 72 as the product of two consecutive integers (8x9). KEEP

We're left with D and E. Since E is not in the correct format (with 1 in the numerator), we can ELIMINATE E Answer:

Re: Which of the following fractions can be written as the difference of r
[#permalink]

Show Tags

20 Aug 2018, 22:58

stonecold wrote:

Which of the following fractions can be written as the difference of reciprocals of two consecutive integers?

A. 1/100 B. 1/121 C. 1/45 D. 1/56 E. 3/72

This is how I solved

let The no be x and x+1 . Which means the reciprocals = 1/x + 1/( X+1) which also means 2 consecutive integer should add upto the no.

Check ans choice and see which no is the multiplication of two consecutive nos eg : a) 100 = 10 * 10 so rule out c) 45 = 7*6 = 42+3 so rule out d) 56 = 7*8 = 56 keep e) 72 = 9*8 = keep

We're left with D and E. Since E is not in the correct format (with 1 in the numerator), we can ELIMINATE E

gmatclubot

Re: Which of the following fractions can be written as the difference of r &nbs
[#permalink]
20 Aug 2018, 22:58