Isosceles trapezoid

Calculate the area of an isosceles trapezoid whose bases are in the ratio of 4:3; leg b = 13 cm and height = 12 cm.

Correct answer:

S =  420 cm2

Step-by-step explanation:

S=(a+c)h/2  a12=b2h2 a1=b2h2=132122=5 cm a=c+2a1 a/c=4:3=4/3 (c+2a1)c=4/3 3(c+2a1)=4c 6a1=c c=6a1=65=30 cm a=c+2a1=30+25=40 cm  S=(a+c)h/2=(40+30)12/2=420 cm2 



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