What is the next number to follow 17, 18, 22, 31, 47, ?

  72

Step-by-step explanation:

First differences are ...

  18 -17 = 1

  22 -18 = 4

  31 -22 = 9

  47 -31 = 16

We observe that these are square numbers. The next square number is 25, so we expect the next number in sequence to be ...

  47 +25 = 72

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take good notes.

do your homework.

use mnemonics and other tricks.

do practice tests.

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