Question

Sameer is collecting stamps. On the first day of the month, he is given 10 stamps. Each week after than he gets 15 more stamps. Which of the following equations defines how many stamps he has after the nth week?

5n + 5

10n + 5

15n - 5

5n + 15

Answer 1

15n-5 is your answer.

Explanation:

1st week => 10 stamps

2nd week => 10 + 15 => 25 stamps

3rd week => 25 + 15 => 40 stamps

common difference = 15

Now,

an = a + (n - 1)d

or, nth week = 10 + (n - 1)15

nth week = 10 + 15n - 15

nth week = 15n - 5