Probability

This topic has expert replies
Master | Next Rank: 500 Posts
Posts: 487
Joined: Fri Mar 27, 2009 5:49 am
Thanked: 36 times

Probability

by dtweah » Sun Jul 05, 2009 2:40 am
The probability that a visit to a primary care physician’s (PCP) office results in neither lab work nor referral to a specialist is 35% . Of those coming to a PCP’s office, 30% are referred to specialists and 40% require lab work. Determine the probability that a visit to a PCP’s office results in both lab work and referral to a specialist.

(A) 0.05
(B) 0.12
(C) 0.18
(D) 0.25
(E) 0.35
Source: — Problem Solving |

User avatar
Site Admin
Posts: 2567
Joined: Thu Jan 01, 2009 10:05 am
Thanked: 712 times
Followed by:550 members
GMAT Score:770

by DanaJ » Sun Jul 05, 2009 6:32 am
This is a classical type of problem involving two characteristics: the first one is lab work, the second is referral to a specialist. When you get such a problem, remember the following formula:

Total = (objects that have trait 1) + (objects that have trait 2) - (objects that have both) + (objects that have none)

In this case, you're presented with percentages. The total will be 100%:

100% = 30% + 40% - x + 35% ---- x will be 5% or 0.05.
Last edited by DanaJ on Mon Jul 06, 2009 9:27 am, edited 1 time in total.

Junior | Next Rank: 30 Posts
Posts: 15
Joined: Sun Jul 13, 2008 6:23 pm

by tryin700 » Sun Jul 05, 2009 9:53 pm
This can also be solved using Venn diagram.

If OA is A

I can provide an explainer.

Master | Next Rank: 500 Posts
Posts: 179
Joined: Tue Jan 08, 2008 7:23 pm
Thanked: 11 times
GMAT Score:590

by nitya34 » Mon Jul 06, 2009 1:39 am
easy 5%


25+x+35=100-35
Many of the great achievements of the world were accomplished by tired and discouraged men who kept on working.

Master | Next Rank: 500 Posts
Posts: 129
Joined: Tue May 19, 2009 9:12 am
Thanked: 8 times

by cata1yst » Mon Jul 06, 2009 7:04 am
DanaJ wrote:This is a classical type of problem involving two characteristics: the first one is lab work, the second is referral to a specialist. When you get such a problem, remember the following formula:

Total = (objects that have trait 1) + (objects that have trait 2) - (objects that have both) - (objects that have none)

In this case, you're presented with percentages. The total will be 100%:

100% = 30% + 40% - x + 35% ---- x will be 5% or 0.05.

Is there an equation for 3 objects? If so, can you explain? Thanks.

Junior | Next Rank: 30 Posts
Posts: 21
Joined: Fri Jun 12, 2009 2:10 pm
Thanked: 1 times

by jakesing » Mon Jul 06, 2009 10:22 am
I believe the formula for 3 is:

Total: (# of 1) + (# of 2) + (# of 3) - (# that have 2 of characteristics) - 2*(# that have all 3) + (# that have none).