Question

A number is selected at random from the numbers 3, 5, 5, 7, 7, 7, 9, 9, 9, 9 The probability that the selected number is their average is

A  \(\frac{1}{10}\)

B  \(\frac{3}{10}\)

C  \(\frac{7}{10}\)

D  \(\frac{9}{10}\)

Answer 1

Total numbers of elementary events are: 10 

Let E be the event of getting selected number being the average

Favorable outcome is = \(\frac{70}{10}\) = 7 

Average = total of observations/ numbers of observation 

Total of observations = 3+ 5+ 5+ 7+ 7+ 7+ 9+ 9 + 9+ 9 = 70 

Numbers of observation = 7 

Numbers of favorable outcomes are: 3 

P ( selecting average number) = P (E) = \(\frac{3}{10}\)