BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Metal bars

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 298
Joined: Tue Feb 16, 2010 1:09 am
Thanked: 2 times
Followed by:1 members

Metal bars

by Deepthi Subbu » Wed Jan 19, 2011 1:02 am
1. An alchemist discovered that the formula to turn ordinary metal into gold is , where G is the number of gold bars and M is the number of metal bars. If a metal bar weighs twice as much as a gold bar, how many metal bars will yield an equal weight of gold?

1. 15
2. 10
3.40
4.30
5. 18

2. 2.A painter intends to mixed two jars of paint to create a new color. He chooses one paint jar randomly from a display containing 2 red and 2 blue samples, and a second jar is chosen at random from a different display containing 3 red and 2 blue samples. If he plans on mixing the two chosen jars together, what is the probability that when mixed together, the result will be purple paint? (The color purple is created with 1 part red and 1 part blue.)

a. 1:2
b. 2:3
c. 3:4
d. 1:1
e. 4:3

OA D for first one and a for second
Top
Source: — Problem Solving |
Junior | Next Rank: 30 Posts
Posts: 26
Joined: Tue Jul 28, 2009 8:12 pm
Thanked: 4 times

by ashis979 » Wed Jan 19, 2011 1:20 am
1. You didn't provide the formula.

2.
There are two ways to get purple paint here: red from the first display and blue from the second or blue from the first and red from the second.

Display 1: Prob. of picking red = 2/4 = 1/2
Display 2: Prob. of picking blue = 2/5
Prob. of picking both to make purple paint = 1/2 * 2/5 = 1/5

Display 1: Prob. of picking blue = 2/4 = 1/2
Display 2: Prob. of picking red = 3/5
Prob. of picking both to make purple paint = 1/2 * 3/5 = 3/10

Therefore, combined prob. = 1/5 + 3/10 = (2+3)/10 = 5/10 = 1/2...Answer = A
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pm
Location: Milpitas, CA
Thanked: 1854 times
Followed by:523 members
GMAT Score:770

by Anurag@Gurome » Wed Jan 19, 2011 1:27 am
Deepthi Subbu wrote:2. 2.A painter intends to mixed two jars of paint to create a new color. He chooses one paint jar randomly from a display containing 2 red and 2 blue samples, and a second jar is chosen at random from a different display containing 3 red and 2 blue samples. If he plans on mixing the two chosen jars together, what is the probability that when mixed together, the result will be purple paint? (The color purple is created with 1 part red and 1 part blue.)
Possible purple combination:
  • 1. RED from 1st set, BLUE from 2nd
    • Number of ways to do it = (Number of ways to select 1 red from 1st set)*(Number of ways to select 1 blue from 1st set) = 2*2 = 4
    1. BLUE from 1st set, RED from 2nd
    • Number of ways to do it = (Number of ways to select 1 blue from 1st set)*(Number of ways to select 1 red from 1st set) = 2*3 = 6
Total number of possibility to result purple = 4 + 6 = 10

Total number of possible selection = (Number of ways to select any one color from 1st set)*(Number of ways to select any one color from 1st set) = (2 + 2)*(2 + 3) = 4*5 = 20

Required probability = 10/20 = 1/2

The correct answer is A.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pm
Location: Milpitas, CA
Thanked: 1854 times
Followed by:523 members
GMAT Score:770

by Anurag@Gurome » Wed Jan 19, 2011 1:41 am
Deepthi Subbu wrote:1. An alchemist discovered that the formula to turn ordinary metal into gold is , where G is the number of gold bars and M is the number of metal bars. If a metal bar weighs twice as much as a gold bar, how many metal bars will yield an equal weight of gold?
If we assume the missing formula as: G = (3/2)M + 15

Tricky Approach:
  • Plug the options.
    A. 15 --> G = (3/2)*15 + 15 --> NOT integer
    B. 10 --> G = (3/2)*10 + 15 = 30 --> Weight mismatch
    B. 40 --> G = (3/2)*40 + 15 = 75 --> Weight mismatch
    B. 30 --> G = (3/2)*30 + 15 = 60 --> CORRECT
Algebraic Approach:
  • Say, required number of metal bar = n and weight of each metal bar = 2w. Hence, total weight of metal bars = 2nw and weight of each gold bar = w.

    Now, from the formula, if M = n, Number of gold bars, G = (3n/2) + 15
    => Total weight of gold bars = Gw = [(3n/2) + 15]w

    According to the problem, Gw = 2nw
    => (3n/2) + 15 = 2n
    => n = 30
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
Top
Newbie | Next Rank: 10 Posts
Posts: 2
Joined: Sun Oct 11, 2009 3:36 am

by joymannasen » Tue Aug 16, 2011 3:48 am
I have a query regarding the interpretation of the probability question. The question asks us to findout the probability that the colour will turn out purpule, where purple is formed by mixing red and blue in the ratio 1:1.
So, I feel that the purple will be formed when we have any of the following combinations

B R
1 1
2 2
3 3
4 4

From my interpretation of the question, i do not see why do we need to pick up only 1 Blue and 1 Red.
Can someone please guide me where I am going wrong.
Top
Post new topic Post Reply
• Page 1 of 1