Question

Q1. the average marks of 4 man is increased by 3. when one of them whose marks are 120, is replaced by another man. what is the marks of new man ..

Q2. SACHIN IN HIS 17TH INNING made a score of 85 runs and then increase his average by 3.what is his average after 17th innings.

Answer 1

1.The average of four men is x, so their overall score is 4x
When a new man comes their average score is x+3, so the overall score is (x+3)*4= 4x+12
If we compare the overall score before (4x) and the overall score now (4x+12) it becomes clear, that the new guy's score is higher by 12 points than the score of the man before him, so 120+12= 132 points.
The answer is: the new man's marks are 132 points.
2.His average before= x
His overall score before= 16x
His average score now=x+3
His overall score now=(x+3)*17=17x+51
16x+85=17x+51
34=x (his average score before)
His average score now is 34+3=37

I think it's ok

Answer 2

1. let the average marks of the 4 men be x. therefore total marks = 4x. now when you replace the man who got 120 marks and replace him by another man who got ,say, y marks. then the average marks becomes x+3. now the total marks is 4x+12. hence 
4x-120+y = 4x+12 => -120+y = 12 => y=132. therefore the other man got 132 marks. 

2. let his average runs after 16 matches be x. hence total runs in 16 matches = 16x. now by scoring 85 runs in the 17th match he increases his average by 3 runs. therefore
16x+85 = 17(x+3) => 16x+85 = 17x+51 => x = 85-51 = 34.
therefore his average runs in 17 matches = x+3 = 37.