URGENT Help is Required ! 2 accidents at 1 day.

Expert replies

navai: Newbie | Next Rank: 10 Posts; Posts: 5; Joined: Thu Aug 26, 2010 7:19 am

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: Beat The GMAT — Quantitative Reasoning | Wed Sep 01, 2010 12:54 pm

sanju09: GMAT Instructor; Posts: 3650; Joined: Wed Jan 21, 2009 4:27 amFollowed by: 80 members; Location: India; Thanked: 267 times; 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

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