abc≠0 and 3/a + 3/b = 3/c. What is the sum a+b? : Data Sufficiency (DS)

My Profile Logout

Test's Subscription Expires:

My Follow Feed Kudos My Error Log

Messages and Replies

Settings Mark All Read

See All

Applicant Notifications

Settings Mark All Read

See All

Global notifications

Settings Mark All Read

See All

abc≠0 and 3/a + 3/b = 3/c. What is the sum a+b?

Sort by Date

Sort by Kudos

Author

Message

TAGS:

Hide Tags

Find Similar Topics

Math Expert

Joined: 02 Sep 2009

Posts: 58340

abc≠0 and 3/a + 3/b = 3/c. What is the sum a+b? [#permalink]

Show Tags

18 May 2017, 00:29

00:00

Difficulty:

35% (medium)

Question Stats:

69% (01:39) correct

31% (01:30) wrong

based on 124 sessions

HideShow timer Statistics

abc≠0 and 3/a + 3/b = 3/c. What is the sum a+b?

(1) ab=c

(2) ab=ac+bc

Spoiler: OA

_________________

What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Signature Read More

Intern

Joined: 26 Jul 2016

Posts: 41

Location: India

Schools: NUS '21 (S), IIMA PGPX"20 (D), IIMC PGPEX"20 (A), NTU '20 (S), German MBA (S)

Re: abc≠0 and 3/a + 3/b = 3/c. What is the sum a+b? [#permalink]

Show Tags

18 May 2017, 00:55

Answer A.

3/a + 3/b = 3/c
1/a + 1/b = 1/c
(a+b)/ab = 1/c
a+b = ab/c
St 1: ab = c ; i.e a+b=1----- sufficient
St 2: ab=ac+bc; ab=c(a+b); a+b=ab/c---- cannot find a+b----- Insufficient.

Director

Joined: 12 Nov 2016

Posts: 701

Location: United States

Schools: Yale '18

GMAT 1: 650 Q43 V37

GRE 1: Q157 V158

GPA: 2.66

Re: abc≠0 and 3/a + 3/b = 3/c. What is the sum a+b? [#permalink]

Show Tags

20 May 2017, 07:37

obliraj wrote:

Answer A.

3/a + 3/b = 3/c
1/a + 1/b = 1/c
(a+b)/ab = 1/c
a+b = ab/c
St 1: ab = c ; i.e a+b=1----- sufficient
St 2: ab=ac+bc; ab=c(a+b); a+b=ab/c---- cannot find a+b----- Insufficient.

It's because if the we know the product of a and b equals the numerator of 1/c or c then the top we can just set equal to a + b= 1

Hence

A

Director

Joined: 04 Sep 2015

Posts: 662

Location: India

WE: Information Technology (Computer Software)

Re: abc≠0 and 3/a + 3/b = 3/c. What is the sum a+b? [#permalink]

Show Tags

05 Feb 2019, 11:49

abc≠0 and 3/a + 3/b = 3/c. What is the sum a+b?

(1) ab=c

(2) ab=ac+bc

solution:
3/a+3/b=3/c =3(a+b)/ab=3/c.

1.ab=c ,substitute in the above equation we get a+b=1.
A is sufficient

2.ab=c(a+b), substitute in equation above, we get 1/c so it provies the same info that we already know. so not sufficient

A is the correct answer.