If a and b are positive integers, a is what percent of b ?

Question

(1) 1/4*b = a
(2) a/b = 20/80

Kurtosis · Answer

St1: b = 4a 
(a/4a)*100 = 25% --> a is 25% of b --> Sufficient

St2: a/b = 1/4 --> Similar to St1 --> Sufficient

Answer: D

NagrajB · Answer

As long as we get the ratio of a over b, we are fine

Each statement gives the same
D

BrentGMATPrepNow · Answer

The solutions provided above are good, so I won't re-solve the question. However, there are a few points to make here. First, always scan both statements BEFORE all else. If one statement looks easier to handle, work on that statement first (for more on this strategy, see our free video - https://www.gmatprepnow.com/module/gmat- ... video/1108) . When we do this and see 20/80 in statement 2, we should be surprised and ask "why didn't they simplify 20/80 to 1/4?" Then we should recognize that statement 1 ALSO has the fraction 1/4 Hmmmmmm! Since these two statements seem remarkably similar, let's see if they are indeed the same. take (1/4)(b) = a and divide both sides by b to get 1/4 = a/b This IS the same as statement 2. IMPORTANT : When BOTH statements provide the SAME information, then the correct answer is EITHER D or E (for more on this concept, see our free video - https://www.gmatprepnow.com/module/gmat- ... video/1109) This is very useful information, because if we don't know how to proceed with this question, we have still narrowed our guess to D or E. Cheers, Brent

mango aadmi · Answer

a, b >0.. a= x%b ?

1) a= b/4...

a=25%, b=100 %.. (S)

2) a/b = 20/80 = 1/4

(S)

so, D

MathRevolution · Answer

Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

If a and b are positive integers, a is what percent of b ?

(1) 1/4*b = a
(2) a/b = 20/80

There are 2 variables (a,b) and 2 equations are given by the conditions, which makes likely that (C) will become the answer.
Looking at the conditions together, condition 1=condition 2 such that 
a becomes 25% of b from b=4a. This is sufficient and the answer becomes (D).

For cases where we need 2 more equations, such as original conditions with “2 variables”, or “3 variables and 1 equation”, or “4 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 70% chance that C is the answer, while E has 25% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since C is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, D or E.

If a and b are positive integers, a is what percent of b ?

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

GMAT Data Sufficiency (DS) Questions

If a and b are positive integers, a is what percent of b ?

Prep Toolkit

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