Question

The second number of and arithmetic sequence is 5. Find the sum of its first and third numbers.

Answer 1

Second number in the arithmetic sequence = 5

Let the first and the third number in the arithmetic sequence be x and y respectively.

Thus, the arithmetic sequence is x, 5, y, …

⇒5 − x = y − 5

⇒ x + y = 5 + 5

⇒ x + y = 10

Therefore, the sum of the first and the third numbers of the arithmetic sequence is 10.