Question

Find the mean of:
(i) First eight natural numbers

(ii) First ten odd numbers

(iii) First five prime numbers

(iv) First six even numbers

(v) First seven multiples of 5.

(vi) Factors of 20

(vii) All prime numbers between 50 and 80

Answer 1

Sol:

(i) First eight natural numbers are:

1,2,3,4,5,6,7 and 8

Therefore, $\text{Mean}=\frac{\text{Sum of numbers}}{\text{Total numbers}}=\frac{1+2+3+4+5+6+7+8}{8}=\frac{36}{8}=4.5$

= Therefore, Mean =4.5}

(ii) First ten odd numbers are: 1, 3, 5, 7, 9, 11, 13, 15, 17 and 19

Therefore, $\text{Mean}=\frac{\text{Sum of numbers}}{\text{Total numbers}}=\frac{1+3+5+7+9+11+13+15+17+19}{10}=\frac{100}{10}=10$

Therefore, Mean =10

(iii) First five prime numbers are : 2,3,5,7,11

Therefore, $\text{Mean}=\frac{\text{Sum of numbers}}{\text{Total numbers}}=\frac{2+3+5+7+11}{5}=\frac{28}{5}=5.6$

Therefore, Mean =5.6

(iv) First six even numbers are: 2, 4, 6, 8, 10, 12

Therefore, $\text{Mean}=\frac{\text{Sum of numbers}}{\text{Total numbers}}=\frac{2+4+6+8+10+12}{6}=\frac{42}{6}=7$

Therefore, Mean = 7

(v) First seven multiples of 5 are: 5, 10,15, 20, 25, 30, 35

Therefore, $\text{Mean}=\frac{\text{Sum of numbers}}{\text{Total numbers}}=\frac{5+10+15+20+25+30+35}{7}=\frac{140}{7}=20$

Therefore, Mean = 20

(vi) Factors of 20 are: 1, 2, 4, 5, 10, 20

Therefore, $\text{Mean}=\frac{\text{Sum of numbers}}{\text{Total numbers}}=\frac{1+2+4+5+10+20}{6}=\frac{42}{6}=7$

Therefore, Mean = 7

(vii) all prime numbers between 50 and 80 are 53, 59, 61, 67, 71, 73, 79

$\text{Mean}=\frac{\text{Sum of numbers}}{\text{Total numbers}}=\frac{53+59+61+67+71+73+79}{7}=\frac{463}{7}=66.1428571$