ΔABC ∼ ΔEDF Area ABC : Area DEF = 49 : 4. If AB, AC, BC are, respectively, 10 cm, 14 cm, 21 cm, then what is the length (in cm) of EF?
Answer & explanation
Correct answer: option 4
We know that,
ΔABC ~ ΔEDF,
We have,
Area ABC ∶ Area DEF = 49 ∶ 4
AB = 10 cm
AC = 14 cm
BC = 21 cm
Area ABC/Area DEF = (AC/EF)2
= 49/4 = (AC/EF)2
= 7/2 = 14/EF
= 1/2 = 2/EF
EF = 4 cm