Average problems for bank exams with solutions

Average Problems with Solutions for SSC and Bank Exams

Q.6.If the mean of 5 observation x, x+2, x+4, x+6 and x+8 is 11, then the mean of the last three observation is :

Solution:

$$ We \ have: \ {(x+(x+2)+(x+4)+(x+6)+(x+8))\over5}=11\ or\ 5x +20 =55 , or\ x = 7 $$

so, the numbers are 7,9,11,13,15.

 $$ ∴ Required\ mean = \ {(11+13+15)\over3}={39\over3} = 13 $$

Q.7.The average of then two digit numbers, which remain the same when the digits interchange their position, is :

Solution:

$$ Average : \ {(11+22+33+44+55+66+77+88+99))\over5} $$

  $$ =\ {(11+99)+(22+88)+(33+77)+(44+66)+55\over9}$$

 $$ =\ {(4\   ×\ 110+55)\over9}={495\over9}=55$$

Q.8. Find the average of all prime number between 30 and 50.

Solution: There are five prime number between 30 and 50.

They are 31, 37, 41, 43 and 47.

$$ Required\ average = \ {31+37++41+43+47\over5}={19\over5}=39.8 $$

Q.9. Find the average of first 40 natural numbers.

Solution:  $$ Sum\ of\ first\  natural\ number =\ {n(n+1)\over2}$$

  $$ So\ Sum\ of\ first\ 40\ natural\ number   ={40×41\over2}=820 $$

∴ Required average = $$ {820\over40}=20.5$$

Q.10. Find the average of first 20 multiple of 7.

  Solution: Required average = $$ ={7(1+2+3+....+20)\over2}={7×20×21)\over20×2}={147\over2}=73.5 $$

For more practice-related average questions, you can visit on the next page.