Missing Term (Geo.)

Free interactive math game: Missing Term (Geo.) — 2, ?, 18. Part of the Sequences category on MathKite.

Example problems

Taken from the generator that powers this exercise. A fresh set appears every time the page is opened, and the printable worksheet holds ten of them.

  1. 6, ?, 24, 48 (Geometric sequence — find the missing term)
  2. 3, 15, ?, 375 (Geometric sequence — find the missing term)
  3. 6, 24, ?, 384 (Geometric sequence — find the missing term)
  4. 2, ?, 8, 16 (Geometric sequence — find the missing term)

About this exercise

A geometric sequence with a hole in the middle.

How to solve it

Find the multiplier from any two neighboring visible terms, then carry it into the hole. When the visible terms stand two apart, the multiplier applied twice must bridge them.

Worked example

In 3, 12, ?, 192 the jump from 3 to 12 is times 4, so the hole holds 12 x 4 = 48.

Common mistake

Bridging with addition. From 12 onward the sequence multiplies, and 48 is the only value that keeps the ratio steady.