Question

Which amount of postage can be formed using just 3-cent stamp and 10-cent stamps?

(a) 27

(b) 20

(c) 11

(d) 5

This question was posed to me in an interview for job.

I need to ask this question from Strong Induction and Well-Ordering topic in section Induction and Recursion of Discrete Mathematics

Answer 1

The correct option is (a) 27

The explanation is: We can form 27 cent of postage with nine 3-cent stamp and 20-cent postage can be formed by using two 10-cent stamps.