Arithmetic Sequences - what is n?

For the sequence with the nth term formula 3n - 1, which term is 29?

• 3rd

  n = 3

• 9th

  n = 9

• 10th

  n = 10

• 11th

  n = 11

Answer explanation

You need to substitute the n numbers into the formula and get 29 as the asnwer. Only one of them works.

This is the same as solving

3n - 1 = 29

For the sequence with the nth term formula 3n + 7, which term is 40?

• 3rd

  n = 3

• 9th

  n = 9

• 10th

  n = 10

• 11th

  n = 11

For the sequence with the nth term formula 5n - 1, which term is 14?

• 5th

  n = 5

• 4th

  n = 4

• 3rd

  n = 3

• 2nd

  n = 2

For the sequence with the nth term formula 6n - 7, which term is 71?

• 13th

  n = 13

• 12th

  n = 12

• 11th

  n = 11

• 10th

  n = 10

For the sequence with the nth term formula 6n + 4, which term is 148?

• 20th

  n = 20

• 24th

  n = 24

• 28th

  n = 28

• 32nd

  n = 32

For the sequence with the nth term formula 3n - 1, which term is 227?

• n = 76

• n = 78

• n = 80

• I am confused

Answer explanation

Solve:

3n - 1 = 227

If you are stuck, then pretend that letter n is an x (and remember solving equations)

Is the number 47 in the sequence 2, 4, 6, 8, 10, 12... ?

• Yes

• No

Is the number 47 in the sequence 2, 6, 10, 14, 18, 22..... ?

• Yes

• No

Is the number 47 in the sequence with the nth term formula 5n -2 ?

• Yes

• No

Answer explanation

Try and solve the equation:

5n - 2 = 47

And if the answer is a whole number, then YES it is in the sequence (because n= 1, 2, 3...).

But if you try and solve it and get a decimal or fraction for n, then 47 cannot be in the sequence.

Is the number 57 in the sequence with the nth term formula 5n - 3 ?

• Yes

• No

Answer explanation

Like the previous question, solve:

5n - 3 = 57

n = whole number means YES

n = not a whole number means NO