|
|
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
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
ModularArithmetic
22 Mar 2015, 14:20
Kudos
Bookmarks
D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
35%
(medium)
Question Stats:
67% (01:17) correct
33%
(01:35)
wrong
based on 110
sessions
History
Date
Time
Result
Not Attempted Yet
In his ranch, Doug Bo can place a loop of rope, called a lasso, once in every 2 throws around a cow’s neck. What is the probability that he will be able to place a lasso around a cow’s neck at least once in 5 attempts?
(A) 1/5
(B) 15/32
(C) 1/2
(D) 31/32
(E) 1
(A) 1/5
(B) 15/32
(C) 1/2
(D) 31/32
(E) 1
FightToSurvive
Joined: 18 Sep 2014
Last visit: 15 Dec 2016
Posts: 198
Given Kudos: 5
Schools: ISB '18 (A) Fisher '19 (II) Smeal Penn State "19 (A$) Kelley '19 (S) Olin '19 (S) Simon '19 (A$) Broad '19 (S)
Products:
22 Mar 2015, 14:27
Kudos
Bookmarks
It's D.
P( putting laaso) =1/2
P ( not putting lasso ) =1/2
Let's assume this person cannot put lasso around cows neck in 5 attempts : P = (1/2)^5=1/32
Then P ( putting lasso a least once) = 1 - (1/32)=31/32.
Hope it's clear.
Posted from my mobile device
P( putting laaso) =1/2
P ( not putting lasso ) =1/2
Let's assume this person cannot put lasso around cows neck in 5 attempts : P = (1/2)^5=1/32
Then P ( putting lasso a least once) = 1 - (1/32)=31/32.
Hope it's clear.
Posted from my mobile device
22 Mar 2015, 18:54
Kudos
Bookmarks
Hi ModularArithmetic,
This prompt is worded in an odd way, but essentially tells us that the probability of lasso-ing a cow is 1/2. The question asks for the probability of lasso-ing a cow AT LEAST ONCE in 5 attempts.
When it comes to probability questions, there are only 2 things that you can calculate: what you WANT to have happen OR what you DON'T WANT to have happen. Those two fractions will always add up to 1. Sometimes it's much easier to calculate what you DON'T WANT and then subtract that fraction from 1 (which will give you the probability of what you DO want).
Here, the work that would be required to calculate 1, 2, 3, 4, and 5 lasso-ings of a cow would take some time and effort. It's far easier to calculate what we DON'T WANT (0 lasso-ings) and subtract that fraction from 1.
The probability of NOT lasso-ing the cow on 5 attempts is:
(1/2)(1/2)(1/2)(1/2)(1/2) = 1/32
1 - 1/32 = 31/32
The probability of lasso-ing a cow AT LEAST ONCE in 5 attempts is 31/32
Final Answer:
GMAT assassins aren't born, they're made,
Rich
This prompt is worded in an odd way, but essentially tells us that the probability of lasso-ing a cow is 1/2. The question asks for the probability of lasso-ing a cow AT LEAST ONCE in 5 attempts.
When it comes to probability questions, there are only 2 things that you can calculate: what you WANT to have happen OR what you DON'T WANT to have happen. Those two fractions will always add up to 1. Sometimes it's much easier to calculate what you DON'T WANT and then subtract that fraction from 1 (which will give you the probability of what you DO want).
Here, the work that would be required to calculate 1, 2, 3, 4, and 5 lasso-ings of a cow would take some time and effort. It's far easier to calculate what we DON'T WANT (0 lasso-ings) and subtract that fraction from 1.
The probability of NOT lasso-ing the cow on 5 attempts is:
(1/2)(1/2)(1/2)(1/2)(1/2) = 1/32
1 - 1/32 = 31/32
The probability of lasso-ing a cow AT LEAST ONCE in 5 attempts is 31/32
Final Answer:
GMAT assassins aren't born, they're made,
Rich
