Geometric Sequence

• Geometric sequence

  A sequence in which a certain number is multiplied to get the next term
• Common ratio


  The number by which each term in a geometric sequence is multiplied to get the next term
• Finding the common ratio

  Divide any term in the sequence by the term that precedes it
• nth term of a geometric sequence


  a1 * r^(n-1), where a1 is the first term and r is the common ratio
• Finding the nth term

  Substitute the first term, common ratio, and term number into the formula
• Finding missing terms in a geometric sequence

  • 3, 12, 48, ? (Answer: 192)
  • ?, 16, 32, 64, 128 (Answer: 8)
• In the initial stages of a measles outbreak, the number of infections can grow geometrically
• If there were 4, 8, 16 infections on the first 3 days, there will be 128 infections on the 6th day