Question

if the side of an equilateral triangle is decresed by 20 % then its area is decresed by....? ​

Answer 1

Answer:

36%

Step-by-step explanation:

let the side of an  equilateral triangle  = a = 100

side  after decreasing                           = a' = 80

area of  an  equilateral triangle         A = [√3/2]a^2 =[√3/2]100^2

area after decreasing                         A'= [√3/2]a'^2 = [√3/2]80^2

PERCENTAGE of decreasing           = [100^2 -80^2]/100^2 x100%

                                                          = [10000 -6400]/10000 x100%

                                                          =3600/10000x100%

                                                          =36%