The perimeter of an isosceles triangle is 91 cm and its base is $1\frac{1}{4}$ times each of its equal sides. What is the length (in cm) of its base?

35

We know that,

Perimeter of an isosceles triangle = 2 × equal side + unequal side

Perimeter of an isosceles triangle = 91cm

Given = Base = \(\frac{5}{4}\)× equal side

Then,

= 91 = 2 × equal side + \(\frac{5}{4}\)× equal side

= $\frac{13}{4}$ × equal side = 91

= Equal side = 28 cm

= Base = \(\frac{5}{4}\)× 28 = 35 cm