Question

Daniel's mean mark for first 3 test is 73. he worked hard for Final test to get mean marks 75. how much should he score to achieve it.

Answer 1

mean = total marks/ no of exams 
73 = total marks/ 3
total marks = 73 x 3 = 219
if mean required is 75
then 
75 = total marks/ 4   
total marks = 300
marks to be scored in the last exam = 300 - 219 = 81

Answer 2

Mean =sum of observation /no. Of observation
73=total marks he obtained /total no. Of test
73=total marks he obtained /3
73×3=total marks he obtained
219=total Marks he obtained in 3 test
Mean =total marks he obtained /total no. Of test
75=total marks he obtained /4
=75×4
=300
Total marks he have to score for mean value 75 for 4 test = 300-219
= 81