Question

The probability that a k-digit code does NOT contain the digits 0, 5 or 9 is

• A. ${0.3}^k$
• B. ${0.6}^k$
• C. ${0.7}^k$
• D. ${0.9}^k$

Answer 1

The correct option is C ${0.7}^k$

Favourable digits to form k digit number = 7

Hence, each place can be filled by 7 ways.

But digits are 10.

So, required Prob $={\left(\frac{7}{10}\right)}^k$