GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 23 Oct 2018, 14:19

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# In a jar there are balls in different colors: blue, red, green and yel

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 50058
In a jar there are balls in different colors: blue, red, green and yel  [#permalink]

### Show Tags

13 Jul 2016, 02:01
00:00

Difficulty:

25% (medium)

Question Stats:

76% (01:48) correct 24% (02:00) wrong based on 131 sessions

### HideShow timer Statistics

In a jar there are balls in different colors: blue, red, green and yellow.
The probability of drawing a blue ball is 1/8.
The probability of drawing a red ball is 1/5.
The probability of drawing a green ball is 1/10.
If a jar cannot contain more than 50 balls, how many yellow balls are in the Jar?

A. 25.
B. 24.
C. 23.
D. 20.
E. 17.

_________________
Retired Moderator
Joined: 26 Nov 2012
Posts: 593
In a jar there are balls in different colors: blue, red, green and yel  [#permalink]

### Show Tags

13 Jul 2016, 03:25
1
2
Bunuel wrote:
In a jar there are balls in different colors: blue, red, green and yellow.
The probability of drawing a blue ball is 1/8.
The probability of drawing a red ball is 1/5.
The probability of drawing a green ball is 1/10.
If a jar cannot contain more than 50 balls, how many yellow balls are in the Jar?

A. 25.
B. 24.
C. 23.
D. 20.
E. 17.

I tried this question without probability formula and used only logic.

We are given that the jar doesn't contain more than 50 balls then we can take that the number can be lesser than 50 or equal to 50.

If we assume exactly 50 numbers of balls we get different incorrect probability.

We need to get some number which is less than 50 and exactly divisible by 8,5 and 10

Lets take LCM of three balls 8,5 and 10 = 40.

The probability of drawing a blue ball is 1/8...For every 8 balls we get 1 BLUE ball then out of 40 balls we get 5 BLUE balls.
The probability of drawing a red ball is 1/5...For every 5 balls we get 1 RED ball then out of 40 balls we get 8 REB balls.
The probability of drawing a green ball is 1/10. For every 10 balls we get 1 GREEN ball then out of 40 balls we get 4 GREEN BALLS.

Then out of 40 - ( 5 + 8 + 4 ) = 23 YELLOW balls.

IMO option C is correct.

OA please...will correct if I missed anything.
Manager
Status: In the realms of Chaos & Night
Joined: 13 Sep 2015
Posts: 154
Re: In a jar there are balls in different colors: blue, red, green and yel  [#permalink]

### Show Tags

13 Jul 2016, 04:01
1
Bunuel wrote:
In a jar there are balls in different colors: blue, red, green and yellow.
The probability of drawing a blue ball is 1/8.
The probability of drawing a red ball is 1/5.
The probability of drawing a green ball is 1/10.
If a jar cannot contain more than 50 balls, how many yellow balls are in the Jar?

A. 25.
B. 24.
C. 23.
D. 20.
E. 17.

The probabilities for blue red and green balls are reduced fractions. Let the no. of yellow balls be x.

A number expressing the probability (p) that a specific event will occur, expressed as the ratio of the number of actual occurrences (n) to the number of possible occurrences (N).

p=$$\frac{n}{N}$$

Total no of balls in the Jar should be the Lease Common Multiple LCM of 8/ 5 & 10 i.e 40

We get $$\frac{5}{40}$$ Blue + $$\frac{8}{40}$$ Red + $$\frac{4}{40}$$ Green + $$\frac{y}{40}$$ = 1

=> Y = 23
Ans is C

Please give kudos for correct ans.
_________________

Good luck
=========================================================================================
"If a street performer makes you stop walking, you owe him a buck"
"If this post helps you on your GMAT journey, drop a +1 Kudo "

"Thursdays with Ron - Consolidated Verbal Master List - Updated"

Director
Joined: 20 Feb 2015
Posts: 793
Concentration: Strategy, General Management
Re: In a jar there are balls in different colors: blue, red, green and yel  [#permalink]

### Show Tags

13 Jul 2016, 08:11
p(yellow)=1-p(remaining)
=1-(1/8+1/5+1/10)
=23/40
no of yellow balls = 23
Target Test Prep Representative
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2830
Re: In a jar there are balls in different colors: blue, red, green and yel  [#permalink]

### Show Tags

08 Nov 2017, 17:43
Bunuel wrote:
In a jar there are balls in different colors: blue, red, green and yellow.
The probability of drawing a blue ball is 1/8.
The probability of drawing a red ball is 1/5.
The probability of drawing a green ball is 1/10.
If a jar cannot contain more than 50 balls, how many yellow balls are in the Jar?

A. 25.
B. 24.
C. 23.
D. 20.
E. 17.

We see that the total number of balls must be a multiple of the LCM of 8, 5, and 10, which is 40. However, since there are no more than 50 balls in the jar, the number of balls must be 40.

Let’s determine the probability of selecting a yellow ball. Since the selected ball will be either blue, red, green, or yellow, we have:

P(blue) + P(red) + P(green) + P(yellow) = 1

1/8 + 1/5 + 1/10 + P(yellow) = 1

5/40 + 8/40 + 4/40 + P(yellow) = 1

17/40 + P(yellow) = 1

P(yellow) = 1 - 17/40 = 23/40

Since the probability of selecting a yellow ball is 23/40, we can create the following proportion to determine the number of yellow balls:

23/40 = y/40

23 = y

Alternative solution:

After we have determined that the total number of balls in the jar must be 40, we can say that the number of blue balls must be 1/8 x 40 = 5, the number of red balls must be 1/5 x 40 = 8, and the number of green balls must be 1/10 x 40 = 4. Thus, the number of yellow balls in the jar must be 40 - (5 + 8 + 4) = 40 - 17 = 23.

_________________

Jeffery Miller

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Re: In a jar there are balls in different colors: blue, red, green and yel &nbs [#permalink] 08 Nov 2017, 17:43
Display posts from previous: Sort by