**Quote:**

There are 4 men of different heights. If the difference among the first 3 men was 2 inch and the difference between the third and fourth was 6 inch and average height was 74. How tall was the 4th man ?

Are you sure you're not paraphrasing the question? If you are, kindly post the actual wording of the question henceforth. It helps users answer your queries more efficiently instead of having to second guess the nature of the question. The problem with the wording of the question is that it mentions a "difference in height". However, this can be interpreted in two ways, with either person being taller and hence can lead to different results.

Assuming you meant that the difference in height between the first and second, and the second and third were respectively 2 inches each, the problem can be solved as follows.

Let the first man's height be

XSecond man's height

= X + 2Third man's height

= (X+2)+2 = X+4Fourth man's height

= X+4+6 = X+10 Average = (Total height of all men)/Number of men

= \frac{X+X+2+X+4+X+10}{4} = \frac{4X + 16}{4} = X+4 = 74 Hence, height of the fourth man

= X+10 = 80Hence the answer is D.