Answer:
A. 22.5 cm, 30 cm and 37.5 cm
Step-by-step explanation:
To find the perimeter of a triangle, all the sides are added together:
A + B + C = Perimeter
Knowing the ratio of the sides, all the sides can be multiplied by a common factor, for the ratio to stay the same. Adding up these factors, setting it equal to a perimeter of 90, and solving:
3x + 4x +5x = 90
12x = 90
x = 7.5 cm
Side Lengths