GMAT Prep #2_DS Tips Word Prob #26

[kwah]

Attached is a question from GMAT Prep Test #2.

What is the most efficient way of achieving the result?

Answer: B

Thanks,
K

[Anurag@Gurome]

Attached is a question from GMAT Prep Test #2.

What is the most efficient way of achieving the result?

Answer: B

Thanks,
K

(1) The amount of the bill was between $15 and $50 implies 15 < bill < 50.
If the bill = $20 then the tip = 2 * 2 = $4 (2 times tens digit) so more than 0.15 * 20 = $3 (15% of the bill)
If the bill = 29$ then the tip would still be 2 * 2 = $4 but here it is less than 0.15 * 29 = $4.5 approx.
No definite answer; NOT sufficient.

(2) The tip calculated by the martin was $8 implies 40 ≤ bill < 50
If the bill is exactly $50, 15% of $50 = 0.15 * 50 = $7.50, which is less than $8.
So the answer to the question is "yes"; SUFFICIENT.

The correct answer is B.

[Bill@VeritasPrep]

For Statement 1, I set up some general guidelines:

.15*$15 = $2.25 tip

$16-$19 = $2 tip

.15*$20 = $3 tip

$20-$29 = $4 tip

.15*$30 = $4.50 tip

$30-$39 = $6 tip

.15 * $40 = $6 tip

$40-$49 = $8 tip

.15 * $50 = $7.50 tip

From this, we can see that the tip could either be more or less than 15 percent depending on the exact amount of the bill. Insufficient

For Statement 2, we know the tip was $8. We can deduce that the total bill must be between $40 and $49. Since 15 percent of $40 is $6 and 15% of 50 is 7.50, the $8 tip is greater than 15 percent no matter what the exact amount of the bill is. Sufficient.