Question

construct a triangle ABC whose perimeter is 9 cm and angles are in the ratio 3:4:5

Answer 1

Let the angles be 3x, 4x and 5x
Therefore,
The sum of all the angles of a triangle are = 180 degrees
Therefore,

3x + 4x + 5x = 180
12x = 180
x = 15

The angles should be (3 × 15) , (4 × 15) , (5 × 15)
Therefore ,
The angles are 45, 60, 75.
Therefore now construction,
Draw a triangle ,
Taking AB as 3cm
Draw two arcs one of 60 and one of 45
Make a Triangle using the angles given

Answer 2

let the angles be 3x :4x:5x
3x+4×+5×=180
12×=180
×=180÷12
x=15

angles are
3x=15×3=45
4×=15×4=60
5×=15×5=75

perimeter=3×side
9=3×?
?=9÷3
?=3