Dr. Cordero

Problem #1:

  • Let the three consecutive odd primes be p, p+2, p+4.
  • Investigate the following question: Is it true that one of the primes p, p+2, p+4 must be divisible by 3?
  • Explore the consequences of a positive answer to the question.

Problem #2:

  • Write out the congruences and make conclusions about the numbers satisfying each.
  • The number is less than 100.
  • Your conjecture should include the number you found.

Problem # 3:

  • First, find a mathematical expression which describes “the number you get when you subtract twice the 1’s digit of n from the number formed by the remaining digits of n”.
  • Prove that if n is divisible by 7, then the expression you just found is divisible by 7.
  • Prove that if the expression you just found is divisible by 7, then n is divisible by 7.