Data Sufficiency

pls give your reasoning

I picked numbers for 1 and found no prices ----> insuf

Did the same for 2, but no quantities ------> insuff

combo:

(10 * 10 - 11 * 40 / 100 ) * 100 Suffic

Condition (1): No information about per sofa cost. So revenue can not be calculated. Hence INSUFFICIENT.

Condition (2): No information about number of sofas sold. So Revenue can not be calculated. Hence INSUFFICIENT.

Combining (1) & (2):

Say x is the number of sofas sold last year.
Then this year, number of sofas sold = 1.1x

Selling price per sofa last year be $y
Total revenue for last year = xy

Selling price per sofa this year = $(30+y)
Total revenue for this year = 1.1x*(30+y)

Percentage increase in revenue

= [[1.1x*(30+y) - xy] / xy] * 100

= [[33x + 1.1xy - xy]/xy ]*100

= [[33 + 0.1y]/y]*100

Y is not known, Hence INSUFFICIENT.

Answer should be E

aks.anupam wrote:Condition (1): No information about per sofa cost. So revenue can not be calculated. Hence INSUFFICIENT.

Condition (2): No information about number of sofas sold. So Revenue can not be calculated. Hence INSUFFICIENT.

Combining (1) & (2):

Say x is the number of sofas sold last year.
Then this year, number of sofas sold = 1.1x

Selling price per sofa last year be $y
Total revenue for last year = xy

Selling price per sofa this year = $(30+y)
Total revenue for this year = 1.1x*(30+y)

Percentage increase in revenue

= [[1.1x*(30+y) - xy] / xy] * 100

= [[33x + 1.1xy - xy]/xy ]*100

= [[33 + 0.1y]/y]*100

Y is not known, Hence INSUFFICIENT.

Answer should be E

what is wrong with what i did above ? I assigend these:

year 1) 10 sofas, each for $10
year 2) 11 sofas, each for $40

combo : 10 *10 = revenue 1st year. 11 * 40 = revenue 2nd year. percent change = new revenue - old revenue / old revenue *100

what is wrong ?

I guess 2 assumptions have been made:

1) You have taken 10 sofas sold for the first year, and
2) You have taken $10 as the cost for first year.

If you take different values, the percentage revenue increase would change!

For check, try putting $ 20 instead of $10:

Percentage increase in first case = (11*40 - 10*10)/100 = 340%

Percentage increase in second case = (11*50 - 10*20)/200 = 175%

heshamelaziry wrote:I picked numbers for 1 and found no prices ----> insuf

Did the same for 2, but no quantities ------> insuff

combo:

(10 * 10 - 11 * 40 / 100 ) * 100 Suffic

Pick a different set of numbers as well! You have to see if the answer will change if you change the numbers you pick! Because if the answer does change, the answer is E!

WHY PICKING NUMBERS HERE DOESN'T WORK ? percentage change should be the same under the given conditions. I tried different values and got answer 340% each time

Kindly see the example I have given above.

xcusemeplz2009 wrote:pls give your reasoning

Always think about what kind of info you would need to answer the question before approaching the statements. The question is asking us for the percent increase in (sofa) sales. This is a value (not a yes/no) question, so we need a single value for sufficiency. Either we need a special equation that relates the sales between the years, or else we actually need to know the sale prices and numbers sold in each year.

Statement One is immediately insufficient as it does not provide us with info about $.

Statement Two is insufficient because we don't know the selling price of last year.

There is no special equation relating sales, and we don't know the acutal sales for each year, or the number sold. Therefore, the answer is E.

But, if at that point, you're not quite convinced, then:
In combination: they sold 10% more sofas and at a rate that is $30 greater than last year. Don't resort to pure algebra here. Quickly pick two different numbers for last year's sale price (and for number sold), and you will see the answer changes. Because we can get multiple values, the statements, even after combination, are not sufficient to answer the question.

Choose E.

heshamelaziry wrote:WHY PICKING NUMBERS HERE DOESN'T WORK ? percentage change should be the same under the given conditions. I tried different values and got answer 340% each time

Picking numbers does work. But you have to do it properly. In DS, you need to pick different kinds of numbers to see if the answer to the question will change.

We have no info about actual price. We know the price of sofas went up by $30. If this was from $20 to $50, we will have a BIG percent increase. But if the price of the sofas went from $500 to $530, our percent increase will be tiny.

Testluv wrote:

xcusemeplz2009 wrote:pls give your reasoning

Always think about what kind of info you would need to answer the question before approaching the statements. The question is asking us for the percent increase in (sofa) sales. This is a value (not a yes/no) question, so we need a single value for sufficiency. Either we need a special equation that relates the sales between the years, or else we actually need to know the sale prices and numbers sold in each year.

Statement One is immediately insufficient as it does not provide us with info about $.

Statement Two is insufficient because we don't know the selling price of last year.

There is no special equation relating sales, and we don't know the acutal sales for each year, or the number sold. Therefore, the answer is E.

But, if at that point, you're not quite convinced, then:
In combination: they sold 10% more sofas and at a rate that is $30 greater than last year. Don't resort to pure algebra here. Quickly pick two different numbers for last year's sale price (and for number sold), and you will see the answer changes. Because we can get multiple values, the statements, even after combination, are not sufficient to answer the question.

Choose E.

if the second statement had given a % increases or decrease is sales price rather than an absolute value increase then the ans would be C (providing statement 1 stayed the same)?

Thanks.

if the second statement had given a % increases or decrease is sales price rather than an absolute value increase then the ans would be C (providing statement 1 stayed the same)?

Thanks.

Yes, in that case C would be the correct answer, and good point.

Testluv wrote:

if the second statement had given a % increases or decrease is sales price rather than an absolute value increase then the ans would be C (providing statement 1 stayed the same)?

Thanks.

Yes, in that case C would be the correct answer, and good point.

Helpful question/answer. Thanks!