A ball is dropped and travels 10 feet in the first second, 25 feet in the second second, and 40 feet in the third second. How many feet will it travel in the seventh second?

The distance traveled in the 1st second is 10 feet.
The distance traveled in the 2nd second is 25 feet.
The distance traveled in the 3rd second is 40 feet.

Let's find the difference between consecutive distances:
$25 - 10 = 15$
$40 - 25 = 15$
Since the difference is constant, this is an arithmetic progression with the first term $a_1 = 10$ and the common difference $d = 15$.

The formula for the $n$-th term is $a_n = a_1 + (n-1)d$.
We need to find the distance traveled during the 7th second, so $n=7$.

Substitute $a_1 = 10$, $d = 15$, and $n=7$ into the formula:

The ball will travel 100 feet during the 7th second.