Maths Questions

A problem in mathematics is given to three students A, B, C and their respective probability of solving the problem is \(1\over 2\), \(1\over 3\) and \(1\over 4\). Probability that the problem is solved is

Solution : Since the probability of solving the problem by A, B and C is \(1\over 2\), \(1\over 3\) and \(1\over 4\) respectively. \(\therefore\)  Probability that problem is not solved is = P(A’)P(B’)P(C’) = (\(1 – {1\over 2}\))(\(1 – {1\over 3}\))(\(1 – {1\over 4}\)) = \(1\over 2\)\(2\over 3\)\(3\over 4\) = \(1\over 4\) = Hence, the […]

A problem in mathematics is given to three students A, B, C and their respective probability of solving the problem is \(1\over 2\), \(1\over 3\) and \(1\over 4\). Probability that the problem is solved is Read More »

The mean and variance of a random variable X having a binomial distribution are 4 and 2 respectively, then P(X = 1) is

Solution : Given that, for binomial distribution mean, np = 4 and variance, npq = 2. \(\therefore\)  q = 1/2, but p + q = 1 \(\implies\) p = 1/2 and n \(\times\) \(1\over 2\) = 4 \(\implies\) n = 8 We know that,  P(X = r) = \(^nC_r p^r q^{n-r}\) \(\therefore\)  P(X = 1)

The mean and variance of a random variable X having a binomial distribution are 4 and 2 respectively, then P(X = 1) is Read More »

Five horses are in a race. Mr A selects two of the horses at random and bets on them. The probability that Mr A selected the winning horse is

Solution : The probability that Mr A selected the lossing horse = \(4\over 5\) \(\times\) \(3\over 4\) = \(3\over 5\) The probability that Mr A selected the winning horse = 1 – \(3\over 5\) = \(2\over 5\) Similar Questions Consider rolling two dice once. Calculate the probability of rolling a sum of 5 or an

Five horses are in a race. Mr A selects two of the horses at random and bets on them. The probability that Mr A selected the winning horse is Read More »

Consider rolling two dice once. Calculate the probability of rolling a sum of 5 or an even sum.

Solution : Sample space of rolling two dice = 36 Now, Event of sum of 5 = { (1,4) (2,3) (3,2) (4,1) } = 4 \(\implies\) probability of getting sum of 5 is 4/36 = 1/9 Now, Event of even sum = { (1,1) (1,3) (1,5) (2,2) (2,4) (2,6) (3,1) (3,3) (3,5) (4,2) (4,4) (4,6)

Consider rolling two dice once. Calculate the probability of rolling a sum of 5 or an even sum. Read More »

The median of a set of 9 distinct observations is 20.5. If each of the largest 4 observation of the set is increased by 2, then the median of the new is

Solution : Median of new set remains the same as of the original set. Similar Questions The mean and variance of a random variable X having a binomial distribution are 4 and 2 respectively, then P(X = 1) is Let \(x_1\), \(x_2\), ….. , \(x_n\), be n observations such that \(\sum{x_i}^2\) = 400 and \(\sum{x_i}\)

The median of a set of 9 distinct observations is 20.5. If each of the largest 4 observation of the set is increased by 2, then the median of the new is Read More »

The mean and the variance of a binomial distribution are 4 and 2, respectively. Then, the probability of 2 success is

Solution : Given that, mean = 4 \(\implies\) np = 4 And Variance = 2 \(\implies\) npq = 2 \(\implies\) 4q = 2 \(\implies\)  q = \(1\over 2\) \(\therefore\)   p = 1 – q = 1 – \(1\over 2\) = \(1\over 2\) Also, n = 8 Probability of 2 successes = P(X = 2) =

The mean and the variance of a binomial distribution are 4 and 2, respectively. Then, the probability of 2 success is Read More »

The probability that A speaks truth is 4/5 while this probability for B is 3/4. The probability that they contradict each other when asked to speak on a fact is

Solution : Given, probabilities of speaking truth are P(A) = \(4\over 5\) and P(B) = \(3\over 4\) And their corresponding probabilities of not speaking truth are P(A’) = \(1\over 5\)  and P(B’) = \(1\over 4\) The probability that they contradict each other = P(A).P(B’) + P(B).P(A’) = \(4\over 5\) \(\times\) \(1\over 4\) + \(1\over 5\)

The probability that A speaks truth is 4/5 while this probability for B is 3/4. The probability that they contradict each other when asked to speak on a fact is Read More »

In a series of 2n observations, half of them equals a and remaining half equal -a. If the standard deviation of the observation is 2, then |a| equal to

Solution : In the 2n observations, half of them equals a and remaining half equal -a. Then, the mean of total 2n observations is equal to 0. \(\therefore\)   SD = \(\sqrt{\sum(x – \bar{x})^2\over N}\) \(\implies\)  4 = \(\sum{x^2}\over 2n\) \(\implies\)  4 = \(2na^2\over 2n\) \(\implies\)  \(a^2\) = 4 \(\therefore\)   a = 2 Similar Questions The

In a series of 2n observations, half of them equals a and remaining half equal -a. If the standard deviation of the observation is 2, then |a| equal to Read More »

A random variable X has poisson distribution with mean 2. Then, P(X > 1.5) equal to

Solution : Now, P(X > 1.5) = P(2) + P(3) + …… \(\infty\) = 1 – [P(0) + P(1)] = 1 – \((e^{-2} + {e^{-2}(2)\over 1})\) = 1 – \(3\over e^2\) Similar Questions The mean and variance of a random variable X having a binomial distribution are 4 and 2 respectively, then P(X = 1)

A random variable X has poisson distribution with mean 2. Then, P(X > 1.5) equal to Read More »

Three houses are available in a locality. Three persons apply for the houses. Each applies for one house without consulting others. The probability that three apply for the same house is

Solution : \(\therefore\)  Total number of cases = \(3^3\) Now, favourable cases = 3(as either all has applied for house 1 or 2 or 3) \(\therefore\) Required Probability = \(3\over 3^3\) = \(1\over 9\) Similar Questions The probability of India winning a test match against the west indies is 1/2 assuming independence from match to

Three houses are available in a locality. Three persons apply for the houses. Each applies for one house without consulting others. The probability that three apply for the same house is Read More »