An easy way to see this is to consider the problem as a toss of a fair coin. Each side has probability 1/2 of occuring. If we toss a coin one time, we have as HEAD=Correct answers the probability 1/2. If we toss it twice we have probability (1/2)^2=1/4. So n is the number of questions on the exam. If there are only 2 questions, we win with the same probability of 1/4. Suppose there are n questions. Then we have (1/2)^n. or 1/2^n. This problem is testing your knowledge of powers of 2 up to 10. It is useful to know 2^10=1024. So you are just comparing 1/1024 and 1/1000. So when n =10 we get a probability that is less than 1/1000 for the first time. All previous n's will give greater probabilities. For example 1/2^5 is 1/32> 1/1000. Of course, any n coming after 10 makes the fraction even smaller But the question wants the SMALLEST of Such N's.mgmt_gmat wrote:n questions can either be true or false. If you answer all n correct you win. What is the least value of n for which the probability is less than 1/1000 for you to win by guessing randomly?
a. 5
b. 10
c. 50
d. 100
e. 1000
Since a question can be either true or false. So probability of getting true or false = 1/2mgmt_gmat wrote:n questions can either be true or false. If you answer all n correct you win. What is the least value of n for which the probability is less than 1/1000 for you to win by guessing randomly?
a. 5
b. 10
c. 50
d. 100
e. 1000
Probability of getting 1 question right = 1/2mgmt_gmat wrote:n questions can either be true or false. If you answer all n correct you win. What is the least value of n for which the probability is less than 1/1000 for you to win by guessing randomly?
a. 5
b. 10
c. 50
d. 100
e. 1000
Probability of getting all correct = (1/2)^n = 1/(2^n)ganesh prasath wrote:y not 2^1000? that ll definitely give the least value right??
