Find the 6th term of the geometric sequence a2 =
-4, r = 1/2

Using only the digits 5, 6, 7, 8, how many different three digit numbers can be formed if no digit is repeated in a number?

Asource of laser light sends rays ab and ac toward two opposite walls of a hall. the light rays strike the walls at points b and c, as shown below: what is the distance between the walls?

Find the sum of the given arithmetic series. 24 + 17 + 10 + 3 + + (–39)