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.
