Question

1. which polygon has a perimeter of 39 cm? (a) 13 cm (b) 8 cm (c) 7 cm 5 cm (d) 6 cm

Explanation:

Step1: Calculate perimeter of option a

For an equilateral triangle with side - length $a = 13$ cm, the perimeter $P=a + a+a=3a$. Substituting $a = 13$ cm, we get $P = 3\times13=39$ cm.

Step2: Calculate perimeter of option b

For a regular pentagon with side - length $b = 8$ cm, the perimeter $P = 5b$. Substituting $b = 8$ cm, we get $P=5\times8 = 40$ cm.

Step3: Calculate perimeter of option c

For a rectangle with length $l = 7$ cm and width $w = 5$ cm, the perimeter $P=2(l + w)=2(7 + 5)=2\times12 = 24$ cm.

Step4: Calculate perimeter of option d

For a regular hexagon with side - length $c = 6$ cm, the perimeter $P = 6c$. Substituting $c = 6$ cm, we get $P=6\times6=36$ cm.

Answer:

A. The equilateral triangle with side - length 13 cm