If a pair of angles placed back to back in tension are connected by one leg of each angle, the net effective area of the section, is

ANS:D -

The answer is correct.

a=effective net cross-sectional area of the connected leg.
b=gross sectional area of outstanding leg(s).

If a single angle in tension is connected by one leg only option (B) would be correct.
Explanation:
K= 3a/3a+b (take out 3 commons from the denominator and simplify further would lead you to the correct answer).

If angles placed back to back and each connected by one leg only option (D) would be correct.
Explanation:
K= 5a/5a+b (taking out 5 from the denominator and further simplification would lead you to correct answer).