Math help?

Question

If you start at 1 and skip count by 3s, what is the 100th number in the sequence

Update:

Why do you have to subtract 2?

Answer 1

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We can set up an arithmetic sequence to describe your number pattern.  I use this general equation to describe the n'th term of such a sequence:

a(n) = a + b(n - 1)

where "a" is the first term (1) and "b" is the common difference (3).  Substitute and simplify to get:

a(n) = 1 + 3(n - 1)

a(n) = 1 + 3n - 3

a(n) = 3n - 2

The 100th term is then:

a(100) = 3(100) - 2

a(100) = 300 - 2

a(100) = 298

Answer 2

1, 4, 7, 10, ...

a_n = 3 n - 2 

a100 = 298

Answer 3

3•100 + 1 = 301