If a/b=2/3 which of the following is not true ?

Question

If  \frac{a}{b}=\frac{2}{3}  which of the following is not true ?

A)  \frac{a+b}{b}=\frac{5}{3}

B)  \frac{b}{b-a}=3

C)  \frac{a-b}{b}=\frac{1}{3}

D)  \frac{2a}{3b}=\frac{4}{9}

E)  \frac{a+3b}{a}=\frac{11}{2}

Bunuel · Accepted Answer

One of the possible values of a and b is a = 2 and b = 3. In this case all options are true but C: (\frac{2-3}{3}=-\frac{1}{3}) eq \frac{1}{3} . Answer: C. Similar question with several different approaches: https://gmatclub.com/forum/if-5x-4y-whi ... 34924.html

carcass · Answer

The fastest approach is just the aforementioned.

a= and b=3 and substitution. ASAP you find the value different, that is the answer.

Regards

JeffTargetTestPrep · Answer

We are given that a/b = 2/3 or 3a = 2b.
 
Let’s simplify each answer choice to determine which one cannot be manipulated to yield 3a = 2b.
 
A) (a + b)/b = 5/3
 
3(a + b) = 5b
 
3a + 3b = 5b
 
3a = 2b
 
Since we have 3a = 2b, answer choice A is not correct. 
 
B) b/(b - a) = 3
 
b = 3(b - a)
 
b = 3b - 3a
 
3a = 2b
 
Since we have 3a = 2b, answer choice B is not correct.
 
C) (a - b)/b = 1/3
 
3(a - b) = b
 
3a - 3b = b
 
3a = 4b
 
Since we have 3a = 4b, answer choice C is correct.
 
Alternative solution:
 
Let’s test each answer choice to determine which one is not true (keep in mind that a/b = 2/3).
 
A) (a + b)/b = 5/3
 
(a + b)/b = a/b + b/b = 2/3 + 1 = 5/3 → This is true.
 
B) b/(b - a) = 3
 
Notice that b/(b - a) = 3 means (b - a)/b = 1/3 when we reciprocate both sides of the equation. 
 
(b - a)/b = b/b - a/b = 1 - 2/3 = ⅓ → This is true.
 
C) (a - b)/b = 1/3
 
(a - b)/b = a/b - b/b = 2/3 - 1 = -1/3 → So (a - b)/b = 1/3 is not true. This is the correct answer choice.
 
Answer: C

KanishkM · Answer

use values, a/b = 2/3

a = 2b / 3, a =2 b = 3

Only C doesn't satisfy when those values are used.

Kinshook · Answer

Given:  \frac{a}{b}=\frac{2}{3}

Asked: which of the following is not true ?

A)  \frac{a+b}{b}=\frac{5}{3} 
 \frac{a+b}{b}= \frac{2+3}{3}= \frac{5}{3} 
TRUE

B)  \frac{b}{b-a}=3 
 \frac{b}{b-a}=3(3-2) = 3 
TRUE

C)  \frac{a-b}{b}=\frac{1}{3} 
 \frac{a-b}{b}=\frac{2-3}{3} = -\frac{1}{3} 
eq \frac{1}{3} 
NOT TRUE

D)  \frac{2a}{3b}=\frac{4}{9} 
 \frac{2a}{3b}=\frac{2*2}{3*3}= \frac{4}{9} 
TRUE

E)  \frac{a+3b}{a}=\frac{11}{2} 
 \frac{a+3b}{a}= = \frac{2+3*3}{2} = \frac{11}{2} 
TRUE

IMO C

Abhishek009 · Answer

Clearly (C)

\frac{2-3}{3}=\frac{-1}{3}

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If a/b=2/3 which of the following is not true ?

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If a/b=2/3 which of the following is not true ?

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