In an examination, 20% of total students failed in Hindi, 70% failed in English and 10% in both. The percentage of these who passed in both the subjects is :
Choose the correct choice from the following answers:
A) 10 %
B) 20 %
C) 30 %
D) 40 %
E) 50 %

Rationale: "pass percentage = 100 - ( 20 + 70 - 10 ) = 100 - 80 = 20 answer : b"
Answer: B