MathDB

Sunny wants to send some secret message to usjl. The secret message is a three digit number, where each digit is one digit from

0

9

(so

000

is also possibly the secret message). However, when Sunny sends the message to usjl, at most one digit might be altered. Therefore, Sunny decides to send usjl a longer message so that usjl can decipher the message to get the original secret message Sunny wants to send. Sunny and usjl can communicate the strategy beforehand. Show that sending a

4

-digit message does not suffice. Also show that sending a

6

-digit message suffices. If it is deduced that sending a

c

-digit message suffices for some

c>6

, then partial credits may be awarded.

C3

Problems(1)