Question

How many numbers with no more than three digits can be formed using only the digits $1$ through $7$ with no digit used more than once in a given number?

• A. 259
• B. 249
• C. 257
• D. 252

Answer 1

Answer: (A)

259

Answer 2

Numbers can be with 1 digit, 2 digit and 3 digit are formed by $1,2,3,4,5,6,7$ $\therefore$ Required numbers $={ }^{7} P_{1}+{ }^{7} P_{2}+{ }^{7} P_{3}=259$