Find the missing number?

A. 1

B. 8

C. 4

D. 7

Answer: Option A

Solution(By Examveda Team)

Splitting the diagram into 3 smaller triangles, with 3 circles each, the sum of the numbers in each smaller triangle is always 21. So,

3 +7 + 11 = 21.
5 + 12 + 4 = 21.
10 + 10 + x = 21.
x = 1.
Missing Number = 1.