BTGmoderatorLU wrote: ↑Fri Feb 05, 2021 3:28 am
Source: Veritas Prep
The probability of snow is the same every day this week, what is the probability of snow on Saturday?
1) The probability of snow on Monday is 1/7
2) The probability having of no snow on both Thursday and Friday is 36/49
The OA is
D
Target question: What is the probability of snow on Saturday?
Given: The probability of snow is the same every day this week
Statement 1: The probability of snow on Monday is 1/7.
If the probability of snow is THE SAME every day this week, then
the probability of snow on Saturday is also 1/7
Since we can answer the
target question with certainty, statement 1 is SUFFICIENT
Statement 2: The probability having of no snow on both Thursday and Friday is 36/49.
Let
p = probability of snow on Saturday.
Since the probability of snow is the same every day this week, we know that p = probability of snow on Thursday and p = probability of snow on Friday.
Also, (1-p) = probability of NO SNOW on Thursday and (1-p) = probability of NO SNOW on Friday.
Statement 2 says: P(no snow on Thursday
AND no snow on Friday) = 36/49
Rewrite as: P(no snow on Thursday)
x P(no snow on Friday) = 36/49
Rewrite as: (1-p)
x (1-p) = 36/49
Simplify: (1-p)² = 36/49
Solve: (1-p) = 6/7
So,
p = 1/7
In other words,
the probability of snow on Saturday is 1/7
Since we can answer the
target question with certainty, statement 2 is SUFFICIENT
Answer: D
Brent Hanneson - Creator of GMATPrepNow.com
