Question

A safe breaker is attempting to crack a safe with a 7 combination code. So far they have worked out that

the first digit is double the third
the code is a palindrome
the fourth number is seven
the third number is one less than the sixth number
the second number is three less than the fourth number
what is the safe combination?

Answer 1

6 4 3 7 3 4 6

Step-by-step explanation:

• Let us denote the digits of the code using letters.

• For a 7-digit code this would be a b c d e f g

• However we are given that the code is a palindrome. So the last 3 digits must be the same as the first 3 digits reversed giving the code as:
  a b c d c b a

• We are given that the 4th number (d) is 7. So this give the combination as
  a b c 7 c b a
  
• The second number(b) is three less than the fourth number
  So b = 7 - 3 = 4. b is also the same s the sixth number so we get
  a 4 c 7 c 4 a
  
• The third number (c) is 1 less than the sixth number
  c = 4 - 1 = 3
  c is also the 5th number
  So..
  a 4 3 7 3 4 a
  
• The first digit(a) is twice the third digit.. First digit same as last
  6 4 3 7 3 4 6