Correct Answer - Option 3 : 25/49
GIVEN:
Girls = 20
Probability of selecting a girl = 2/5
CONCEPT:
For 'or' addition function is applied.
FORMULA USED:
P = Favorable outcomes/Total outcomes
nCr = n!/r!(n - r)!
CALCULATION:
Let there be x boys in the class.
A.T.Q
20/(20 + x) = 2/5
⇒ 100 = 40 + 2x
⇒ x = 30
Total students = 50
Probability of 2 girls = 20C2/50C2 = 190/1225
Probability of 2 boys = 30C2/50C2 = 435/1225
Required probability = 190/1225 + 435/1225 = 25/49
∴ The probability is 25/49.