If there is a bag containing less than 30 balls, how many of them are

Question

If there is a bag containing less than 30 balls, how many of them are red balls?

(1) The probability of picking a red ball from the bag is  \frac{1}{10} .
(2) There are 10 blue ball in the bag.

source : self made

chetan2u · Accepted Answer

Hi.. The question is correct as it is... 1) statement tells probability is 1/10 So if total is <=30, total number could be 10,20 or 30 If total is <30, total can be 10 or 20 2) statement II tells us that blue is 10 if total is 30, red is 3 and if total is 20 red is 2. Insufficient Combined... If total can be 10,20,30 and blue is 10, total will be >10 as there is at least one red.. But if total <30 and >10, total can be only 20, so red is 2.. Blue -10, red-2 and other colours/colour-8 ( we are not concerned what other colours are, we are only concerned with red) So sufficient C

niks18 · Answer

Total balls  <30

Statement 1 : implies ratio of number of red balls to total number of balls  = 1:10 . so let total red balls be  x  and total number of balls be  10x

given  10x<30=> x<3

So red balls can be  1  or  2  and total number of balls can be  10  or  20 . So No unique answer.  Insufficient

Statement 2 : Nothing mentioned about red balls.  Insufficient

Combining 1 & 2 we know total number of blue balls is  10 , so total number of balls has to be  20 . Hence number of red balls is  2 .  Sufficient

Option  C

arichinna · Answer

Just a small correction in the last bit:   
 
Combining 1 & 2 we know total number of blue balls is 10, so total number of red balls has to be less than 20 (because total balls is less than 30). Hence number of red balls is 1.

atreyu79 · Answer

Good Morning

I do not agree. Nowhere it is mentioned that the bag has only red and blue balls

niks18 · Answer

Hi  arichinna

Thanks for highlighting but I feel the the question needs to be changed to less than or equal to 30, other wise statement 1 will not hold

niks18 · Answer

Hi  atreyu79

You do not need to know how many types of balls are there. You simply need to know total number of balls and relationship between total number of balls and number of red balls. this information can be arrived at by combining both the statements.
However I also feel a slight correction needs to be made in the question stem. the bag must have less than OR EQUAL to 30 balls.

bumpbot · Answer

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.

If there is a bag containing less than 30 balls, how many of them are

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 there is a bag containing less than 30 balls, how many of them are

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