JAMB Mathematics Past Questions & Answers - Page 292

1,456.

Find the standard deviation of the following data -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5

A.

2

B.

3

C.

\(\sqrt{10}\)

D.

\(\sqrt{11}\)

Correct answer is C

x = \(\frac{\sum x}{N}\)

= \(\frac{0}{11}\)

= 0

\(\begin{array}{c|c} x & (x - x) & (x - x)^2 \\\hline -5 & -5 & 25 \\ -4 & -4 & 16 \\-3 & -3 & 9 \\ -2 & -2 & 4 \\ -1 & -1 & 1\\ 0 & 0 & 0\\ 1 & 1 & 1\\ 2 & 2 & 4\\ 3 & 3 & 9\\ 4 & 4 & 16 \\5 & 5 & 25\\ \hline & & 110\end{array}\)
S.D = \(\sqrt{\frac{\sum(x - x)^2}{\sum f}}\)

= \(\sqrt{\frac{110}{11}}\)

= \(\sqrt{10}\)

1,457.

A number is selected at random between 10 and 20, both numbers inclusive. Find the probability that the number is an even number

A.

\(\frac{5}{11}\)

B.

\(\frac{1}{2}\)

C.

\(\frac{6}{11}\)

D.

\(\frac{7}{10}\)

Correct answer is C

n(even numbers between 10 and 20 inclusive) = 6

n(numbers between 10 and 20) = 11

P(even) = \(\frac{6}{11}\)

1,458.

In a basket of fruits, there are 6 grapes, 11 bananas and 13 oranges, if one fruit is chosen at random, what is the probability that the fruit is either a grape or a banana?

A.

\(\frac{17}{30}\)

B.

\(\frac{11}{30}\)

C.

\(\frac{6}{30}\)

D.

\(\frac{5}{30}\)

Correct answer is A

Pgrape or Pbanana = \(\frac{6}{30}\) + \(\frac{11}{30}\)

= \(\frac{17}{30}\)

1,459.

Find the difference between the range and the variance of the following set of numbers 4, 9, 6, 3, 2, 8, 10, 5, 6, 7 where \(\sum d^2\) = 60

A.

2

B.

3

C.

4

D.

6

Correct answer is A

Range : 10 - 2 = 8

Variance = \(\frac{\sum d^{2}}{n}\)

= \(\frac{60}{10}\)

= 6

8 - 6 = 2.