The ratio of the angle measures of a triangle is 1: 3: 5. find the angle measures. then classify the triangle by its angle measures

A triangle has 180 degrees.  You can find the total sum of the ratio by adding its parts together 1+3+5 = 9  Now to find out what each part of the ratio is worth we divide the whole value (180) by the sum of the ratio parts (9)
180/9 = 20

Now we multiply each part of the ratio by 20
1 * 20 = 20
3 * 20 = 60
5 * 20 = 100

Since we have an angle greater than 90 degrees this is an obtuse triangle.