GMAT Question of the Day: Daily via email | Daily via Instagram New to GMAT Club? Watch this Video

 It is currently 03 Aug 2020, 10:40

### 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

# The snipers shoot a certain target. Their probabilities of

Author Message
SVP
Joined: 21 Jan 2007
Posts: 1856
Location: New York City
The snipers shoot a certain target. Their probabilities of  [#permalink]

### Show Tags

04 Nov 2007, 00:24
The snipers shoot a certain target. Their probabilities of hitting the target are 0.9, 0.7, and 0.5 respectively. The snipers make one salvo. What is the probability:

1. that exactly one sniper missed?
2. that exactly one sniper hit?
3. that exactly two snipers missed?
4. that exactly two snipers hit?

--== Message from the GMAT Club Team ==--

THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION.
This discussion does not meet community quality standards. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Intern
Joined: 01 Nov 2007
Posts: 49

### Show Tags

04 Nov 2007, 04:42
I feel Q1 and Q4 & Q2 and Q3 are the same. Arent they?

I mean if exactly one missed the other two hit and when exactly one hit the other two missed.

And is the answer of Q1 = 0.485 and that of Q2 = 0.185.

If so I can provide my explanation

SVP
Joined: 21 Jan 2007
Posts: 1856
Location: New York City

### Show Tags

18 Nov 2007, 16:51
Proababilty that Sniper 1 misses and other 2 hit = (1-0.9) (0.7) (0.5) = 0.1 * 0.7 * 0.5

Probability that Sniper 2 misses and other 2 hit = (0.9) (1-0.7) (0.5) = 0.9 * 0.3 * 0.5

Probability that sniper 3 misses and other 2 hit = (0.9) (0.7)(1-0.5) = 0.9 * 0.7 * 0.5

Therefore Probability that exactly 1 sniper misses = .1(.7)(.5)+.9(.7)(.5)+.9(.3)(.5)

see any errors?
Senior Manager
Joined: 13 Dec 2006
Posts: 297
Location: Indonesia

### Show Tags

18 Nov 2007, 16:58
yep, I do

Following is my explanation:

1. Exacty one sniper missed = 0.9*0.7*0.5 + 0.9*0.3*0.5 + 0.1*0.7*0.5 = 0.485

2. Exactly one sniper hit= 0.9*0.3*0.5 + 0.1*0.7*0.5 + 0.1*0.3*0.5 =0.185

3. Exactly two sniper missed = Exactly one snipper hit

4. Exactly two snipers hit = one sniper missed

Amar
SVP
Joined: 21 Jan 2007
Posts: 1856
Location: New York City

### Show Tags

03 Dec 2007, 07:22
Amardeep Sharma wrote:
yep, I do

Following is my explanation:

1. Exacty one sniper missed = 0.9*0.7*0.5 + 0.9*0.3*0.5 + 0.1*0.7*0.5 = 0.485

2. Exactly one sniper hit= 0.9*0.3*0.5 + 0.1*0.7*0.5 + 0.1*0.3*0.5 =0.185

3. Exactly two sniper missed = Exactly one snipper hit

4. Exactly two snipers hit = one sniper missed

Amar

very nice.
SVP
Joined: 21 Jan 2007
Posts: 1856
Location: New York City
Re: joint Probability - salvo  [#permalink]

### Show Tags

03 Dec 2007, 07:32
The snipers shoot a certain target. Their probabilities of hitting the target are 0.9, 0.7, and 0.5 respectively. The snipers make one salvo. What is the probability that at least 1 sniper missed?
Senior Manager
Joined: 25 Oct 2006
Posts: 380
Re: joint Probability - salvo  [#permalink]

### Show Tags

17 Aug 2008, 11:41
(1)that exactly one sniper missed = (4) that exactly two snipers hit = 0.9*0.7*0.5 + 0.9*0.3*0.5 + 0.1*0.7*0.5 = 0.485
(2)that exactly one sniper hit = (3) that exactly two snipers missed = 0.9*0.3*0.5 + 0.1*0.7*0.5 + 0.1*0.3*0.5 =0.185
all three missed = 0.1*0.3*0.5

At least one missed = Exactly one missed + exactly two missed + all three missed = 0.485 + 0.185 + 0.015 = 0.685
Manager
Joined: 14 Jun 2008
Posts: 137

### Show Tags

17 Aug 2008, 23:01
Amardeep Sharma wrote:
yep, I do

Following is my explanation:

1. Exacty one sniper missed = 0.9*0.7*0.5 + 0.9*0.3*0.5 + 0.1*0.7*0.5 = 0.485

2. Exactly one sniper hit= 0.9*0.3*0.5 + 0.1*0.7*0.5 + 0.1*0.3*0.5 =0.185

3. Exactly two sniper missed = Exactly one snipper hit

4. Exactly two snipers hit = one sniper missed

Amar

should you multply each of the above by 1/3
for e.g.
Exacty one sniper missed = 1/3(0.9*0.7*0.5) + 1/3(0.9*0.3*0.5) + 1/3(0.1*0.7*0.5)
as each of the three events have a probability of occuring 1/3

--== Message from the GMAT Club Team ==--

THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION.
This discussion does not meet community quality standards. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Re:   [#permalink] 17 Aug 2008, 23:01