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Percentages

by divyasood11 » Tue Dec 09, 2014 9:50 am
Hello

Please help me out with the following problems:

1. What is the % reduction in sale price of gum balls purchased on a sale?
a) At the sale, gumballs that regularly sell for $0.60 each are on sale at two for $0.90
b) At the sale, the price of three gumballs before reduction is equal to price of four gumballs after reduction


2. In an examination conducted for a class, having only two questions, what % of the class answered both questions incorrectly?
a. 60% of class did not answer the first question correctly
b. 70% did not answer the second question of the test correctly.

OA1- D
OA2- E


Thank You
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Source: — Data Sufficiency |
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by GMATinsight » Wed Dec 10, 2014 2:04 am
divyasood11 wrote:Hello

Please help me out with the following problems:

1. What is the % reduction in sale price of gum balls purchased on a sale?
a) At the sale, gumballs that regularly sell for $0.60 each are on sale at two for $0.90
b) At the sale, the price of three gumballs before reduction is equal to price of four gumballs after reduction


2. In an examination conducted for a class, having only two questions, what % of the class answered both questions incorrectly?
a. 60% of class did not answer the first question correctly
b. 70% did not answer the second question of the test correctly.

OA1- D
OA2- E


Thank You
It's in best interest of reader to see the different questions as separate posts.
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by GMATinsight » Wed Dec 10, 2014 2:10 am
divyasood11 wrote:
1. What is the % reduction in sale price of gum balls purchased on a sale?

a) At the sale, gumballs that regularly sell for $0.60 each are on sale at two for $0.90
b) At the sale, the price of three gumballs before reduction is equal to price of four gumballs after reduction

OA1- D



Thank You
Question: %age Reduction in Sale Price = (Last price - Regular price)x100/Regular price = ?

Statement 1: At the sale, gumballs that regularly sell for $0.60 each are on sale at two for $0.90

i.e Regular Price = 0.6
Last price = two for 0.9 i.e. 0.9/2 = 0.45

i.e. %age Reduction in Sale Price = (Last price - Regular price)x100/Regular price
%age Reduction in Sale Price = (0.45-0.6)x100 / 0.6 = 25% i.e. Unique value
Hence Sufficient

Statement 2: At the sale, the price of three gumballs before reduction is equal to price of four gumballs after reduction

3x(Regular Price) = 4x(Last price)
i.e. Last Price = 0.74 x Regular Price

i.e. %age Reduction in Sale Price = (Last price - Regular price)x100/Regular price
%age Reduction in Sale Price = [RP-(0.75xRP)]x100 / RP = 25% i.e. Unique value
Hence Sufficient

Answer: Option D
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by GMATinsight » Wed Dec 10, 2014 2:18 am
divyasood11 wrote:
2. In an examination conducted for a class, having only two questions, what % of the class answered both questions incorrectly?
a. 60% of class did not answer the first question correctly
b. 70% did not answer the second question of the test correctly.

OA2- E


Thank You
Question: % of class answered both correctly = ?

The best method is to make Double Matrix and solve however it can be solved this way as well

Only first correct + only Second Correct + both correct + none correct = 100%

Statement 1: 60% of class did not answer the first question correctly
i.e. only Second Correct none correct = 60%
i.e. Only first correct + both correct = 40%

But Only first correct is unknown so

Not Sufficient

Statement 2: 70% did not answer the second question of the test correctly.
Only first correct + none correct = 30%
i.e. only Second Correct + both correct = 70%

But Only Second correct is unknown so

Not Sufficient

Combining the two statements

only Second Correct + both correct = 70%
Only first correct + both correct = 40%

But still we can't figure out the Both correct case

Hence Not Sufficient

Answer: Option E
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by GMATinsight » Wed Dec 10, 2014 2:23 am
divyasood11 wrote:
2. In an examination conducted for a class, having only two questions, what % of the class answered both questions incorrectly?
a. 60% of class did not answer the first question correctly
b. 70% did not answer the second question of the test correctly.

OA2- E
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by mbawisdom » Wed Dec 17, 2014 9:23 am
QUESTION 1:

We need to know the regular price (RP) and the sale price (SP) as % reduction = (RP - SP)/RP

Statement 1: RP = $0.60; SP = $0.45 (if you buy two) - SUFFICIENT

Statement 2: 3.RP = 4.SP; gives us SP = 3/4 RP
We can plug SP into our equation above for % reduction -->% reduction = (RP - SP)/RP
% reduction = (RP - 3/4.RP)/RP = 1/4

Therefore SUFFICIENT


QUESTION 2

We need to know the % of the class that answered both questions incorrectly

Statement 1: Only tells us about question 1 and therefore is INSUFFICIENT
Statement 2: Only tells us about question 2 and therefore is INSUFFICIENT

What about the statements together?

From statement 1: 60% got question 1 incorrect
From statement 2: 70% got question 2 incorrect

Unfortunately we don't know how these two statements intersect (or overlap) so INSUFFICIENT together
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