URGENT Help is Required ! 2 accidents at 1 day.

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
This topic has expert replies
Newbie | Next Rank: 10 Posts
Posts: 5
Joined: Thu Aug 26, 2010 7:19 am

URGENT Help is Required ! 2 accidents at 1 day.

by navai » Wed Sep 01, 2010 12:54 pm
Guys , sorry if i am writing in a wrong place with a wrong question. but I have a retake tomorrow and if you could help me to sort it out i would be very very thankful for it! Really.

There is the question :
On average at a certain road junction there are 3 accidents per month. if we take a month as defined as exactly 30 days, what is the probability of there being 2 or more accidents on any day?

The correct answer is 0.0047

But I dont know how to solve it. and i have to know it before tomorrow's exam.
Please guys dont let me get in trouble
Source: — Quantitative Reasoning |

User avatar
GMAT Instructor
Posts: 3650
Joined: Wed Jan 21, 2009 4:27 am
Location: India
Thanked: 267 times
Followed by:80 members
GMAT Score:760

by sanju09 » Thu Sep 02, 2010 4:00 am
navai wrote:Guys , sorry if i am writing in a wrong place with a wrong question. but I have a retake tomorrow and if you could help me to sort it out i would be very very thankful for it! Really.

There is the question :
On average at a certain road junction there are 3 accidents per month. if we take a month as defined as exactly 30 days, what is the probability of there being 2 or more accidents on any day?

The correct answer is 0.0047

But I dont know how to solve it. and i have to know it before tomorrow's exam.
Please guys dont let me get in trouble

Proportionally, there is 1 accident every 10 days, hence on a given day, there are 1/10 chance that 1 accident would take place, 1/10 × 1/10 chance that 2 accidents would take place, and 1/10 × 1/10 × 1/10 chance that 3 accidents would take place.

Hence, the probability of there being 2 or more accidents on any day

= probability that 2 accidents would take place + probability that 2 accidents would take place

= 1/10 × 1/10 + 1/10 × 1/10 × 1/10

= 1/1000 + 1/100

= 11/1000

= I am not getting 0.0047

= sorry, for this not coming up before your tomorrow's exam
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com