Aramp leads up to a building. the top of the ramp is 5 feet above the ground, and the bottom is 15 feet from the building as shown.

what is the length of the ramp? round your answer to the nearest tenth of a foot.

a.
15.8 ft

b.
14.1 ft

c.
16.0 ft

d.
20.0 ft

To answer this you have to use Pythagoras's theorem: a^2 + b^2 = c^2

Put in the values:
5^2 + 15^2 = c^2

Simplify it:
25 + 225 = c^2

Simplify again:
250 = c^2

Square root both sides:
15.8113883008 = c

So the ramp is:
15.8113883008 feet

Now round the number: 
15.8ft

The above is the answer :)
(btw sorry in advance if you've spotted a mistake)