What is the value of 1/k + 1/r ? (1) k + r = 20 (2) kr = 64

Question

What is the value of  \frac{1}{k} + \frac{1}{r}  ?

(1)  k + r = 20

(2)  kr = 64

thulu96 · Answer

1/k + 1/r = (k +r)/kr 
=> C. Both statements together are sufficient

KSBGC · Answer

\frac{1}{k} + \frac{1}{r}

=  \frac{k+r}{kr}

Statement 1 : k + r = 20. NOT sufficient . we don't know the value of kr.

Statement 2 : The same as 1. k + r is unknown.

(1+2) : Sufficient. we have the value of kr and k + r.

The best answer is C.

Kinshook · Answer

Asked: What is the value of  \frac{1}{k} + \frac{1}{r}  ?
  \frac{1}{k} + \frac{1}{r} 
 =\frac{k + r}{kr}

(1)  k + r = 20 
Since kr is unknown
NOT SUFFICIENT

(2)  kr = 64 
Since k + r is unknown
NOT SUFFICIENT

(1) + (2)
(1)  k + r = 20 
(2)  kr = 64 
 \frac{1}{k} + \frac{1}{r} 
 =\frac{k + r}{kr} 
 =\frac{20}{64} 
 =\frac{5}{16} 
SUFFICIENT

IMO C

DavidTutorexamPAL · Answer

answer with zero calculations 
the only thing we need is the following rule: if we have the same or more equations than variables, we can find the variable's value.

in order to answer the question, we need the value of both variables. 
1) and 2) are each, on their own, an equation with two variables = infinite solutions, insufficient! 
Together - 2 equations with 2 variables ==> definitely solvable! sufficient!

bumpbot · Answer

Automated notice from GMAT Club BumpBot: 

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

 This post was generated automatically.

What is the value of 1/k + 1/r ? (1) k + r = 20 (2) kr = 64

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards