Answer:
20cm
Step-by-step explanation:
for the triangle:
Perimeter = 30cm
a + a + a = 30
3a = 30
hence a = 10cm
For the rectangle:
Perimeter = 30cm
a + a + b + b = 30
but a = 10cm
10 + 10 + b + b = 30
20 + 2b = 30
2b = 10
hence b = 5cm
Perimeter of square = b + b + b + b
= 5 + 5 + 5 + 5 = 20cm
