Question

Is 100,20,4 arithmetic?

Answer 1

No. The sequence is not arithmetic, but rather geometric.

Explanation:

Arithmetic Sequence

Arithmetic Sequence is a sequence that has common difference.

To find a common difference:-

`\displaystyle \large{a_(n + 1) - a_n = d}`

Thus:-

20-100 = -80

4-20 = -16

Since both are not common, the sequence is not arithmetic.

Geometric Sequence

Geometric Sequence is a sequence that has common ratio.

To find a common ratio:-

`\displaystyle \large{ (a_(n + 1))/(a_n) = r}`

Thus:-

20/100 = 1/5

4/20 = 1/5

Since both are common, the sequence is geometric.

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