Posted by **Anonymous- boy** on Friday, February 17, 2012 at 5:52pm.

in triangle ABC, the size of angle B is 5 times the size of angle A and the size of angle C is 9 degrees less than 4 times the size of angle A

Find the size of angle A

- algebra -
**MathMate**, Friday, February 17, 2012 at 6:09pm
You can set up the equations as follows:

B=5A

C=4A-9

A+B+C=180 (sum of angles of a triangle).

and solve for A, B and C.

However, you can easily solve it by substitution into the third equation:

A+B+C=180

A + 5A + 4A-9 = 180

10A=189

A=18.9

With A known, you can then find the remaining angles by substitution into the first two equation.

- algebra -
**MathGuru**, Friday, February 17, 2012 at 6:12pm
The sum of the angles of a triangle are 180 degrees.

Therefore:

Let x = angle A

5x = angle B

4x - 9 = angle C

Equation:

x + 5x + 4x - 9 = 180

Solve for x.

## Answer This Question

## Related Questions

- algebra - In triangle ABC, the size of angle B is 5 times the size of angle A, ...
- geometry - In a triangle ABC, angle B is 3 times angle A and angle C is 8 ...
- Algebra - In a triangle ABC, angle B is three times angle A and angle C is 5 ...
- algebra - In a triangle ABC , angle B is 4 times angle A and angle C is 17 ...
- math - In a triangle ABC,angle B is 3 times angle A and angle C is 5 degrees ...
- algebra 1 - In a triangle ABC,angle b is 4 times angle "A" and angle "C" IS 17 ...
- algebra 1 - In a triangle ABC,angle b is 4 times angle "A" and angle "C" IS 17 ...
- mat116 - In a triangle ABC, angle B is 4 times angle A and angle C is 16 degrees...
- MATH - In a triangle ABC, angle B is three times angle A and angle C is 1 less ...
- math - In a triangle ABC, angle B is 5 times angle A and angle C is 18° less ...

More Related Questions