Let the length of the base of this isosceles triangle be = x
One of its equal sides = 3x
Another one of its equal sides = 3x
Their perimeter = x + 3x + 3x = 21 cm
To find the value of each side let us first solve this equation .
= x + 3x + 3x = 21 cm
= 7x = 21 cm
= x = 21 ÷ 7 ( transposing ×7 from LHS to RHS changes ×7 to ÷7 )
= x = 3
Then length of base = 3 cm
Length of one equal side = 3 × 3 = 9 cm
Length of another equal side = 3 × 3 = 9 cm
Therefore , the the three sides of this triangle = 3 cm , 9 cm and 9cm .
