NDA/NA SOLVED PAPER 2015-I (MATHEMATICS)

Total Questions: 120

91. The mean and the variance 10 observations are given to be 4 and 2 respectively. If every observation is multiplied by 2, the mean and the variance of the new series will be respectively

Correct Answer: (c) 8 and 8
Solution:

92. Which one of the following measures of central tendency is used in construction of index numbers?

Correct Answer: (b) Geometric mean
Solution:Geometric mean is used in construction of index numbers.
∴ option (b) is correct.

93. The correlation coefficient between two variables X and Yis found to be 0.6. All the observations on X and Y are transformed using the transformations U = 2 - 3X and V = 4 Y + 1 The correlation coefficient between the transformed variables Uand will be

Correct Answer: (c) -0.6

94. Which of the following statements is/are correct in respect of regression coefficients?

1. It measures the degree of linear relationship between two variables.
2. It gives the value by which one variable changes for a unit change in the other variable.

Select the correct answer using the code given below.

Correct Answer: (b) 2 only
Solution:It gives the value by which one variable changes for a unit change in the other variable.
∴ option (b) is correct.

95. A set of annual numerical data, comparable over the years, is given for the last 12 years.

1. The data is best represented by a broken line graph, each corner (turning point) representing the data of one year.
2. Such a graph depicts the chronological change and also enables one to make a short-term forecast.

Which of the above statements is/are correct?

Correct Answer: (c) Both 1 and 2
Solution:The annual numerical data for comparable for last 12 years is represented by broken line graph, where each turning point represent the data of a particular year, while such graph do not depict the chronological change.
∴ Option (c) is correct.

96. Two men hit at a target with probabilities 1/2 and 1/3 respectively. What is the probability that exactly one of them hits the target?

Correct Answer: (a) 1/2
Solution:

97. Two similar boxes Bᵢ (i = 1, 2) contain (i + 1) red and (5 - i - 1) black balls. One box is chosen at random and two balls are drawn randomly. What is the probability that both the balls are of different colours?

Correct Answer: (d) 3/5

98. In an examination, the probability of a candidate solving a question is 1/2 Out of given 5 questions in the examination, what is the probability that the candidate was able to solve at least 2 questions?

Correct Answer: (d) 13/16
Solution:

99. If A ⊆ B , then which one of the following is not correct?

Correct Answer: (c)

100. mean and the variance in a binomial distribution are found to be 2 and 1 respectively. The probability P(X = 0) is

Correct Answer: (d) 1/16
Solution: