Question:
The measures of two complementary angles have a ratio of 3 : 2. What is the measure of the larger angle?
—————
Solution:
Call those two angles x and y, where x is the larger one.
If they are complementary, then their sum equals 90°:
x + y = 90° (i)
Also, the ratio between x and y is 3 : 2, so
x 3
—— = ——
y 2
Product of the extremes = product of the means:
2x = 3y
2x – 3y = 0 (ii)
Now, just solve this system of equations:
x + y = 90° (i)
2x – 3y = 0 (ii)
Solve it with elimination. Since you want to know the value of the larger angle, which is x, then eliminate the variable y by doing the following:
Multiply the equation (i) by 3,
3x + 3y = 270° (iii)
2x – 3y = 0 (ii)
then add both equations, so you cancel out the variable y:
3x + 2x + 3y – 3y = 270° + 0
3x + 2x = 270°
5x = 270°
270°
x = ———
5
x = 54° <——— this is the measure of the larger angle.
I hope this helps. =)
Tags: system of linear equations elimination method solve complementary angles algebra geometry