Find Missing Number?

A. 2

B. 1

C. 4

D. 3

Answer: B

Solution:

Sum of all the numbers in each box is 35.

1st circle

3 + 17 + 4 + 11 = 35

2nd circle

2 + 16 + 7 + 10 = 35

3rd circle

6 + 13 + ? + 15 = 35

⇒34 + ? = 35

⇒ ? = 35 – 34

⇒ ? = 1