Answer:
2.4cm
Step-by-step explanation:
the area of a triangle is
baseline × height / 2
that means two lengths of the triangle have to be multiplied.
and to have 2 similar triangles means that all lengths inside one triangle are the corresponding lengths inside the other triangle multiplied by the scaling factor f.
multiplying 2 if these lengths with each other means also including the square of the scaling factor (multiplying with the scaling factor twice).
so, if the area of triangle 1 is
"baseline 1" × "height 1" / 2 = 45 cm²
then the area of triangle 2 is
"baseline 2" × "height 2" / 2 =
= "baseline 1"×f × "height 1"×f /2 =
= "baseline 1" × "height 1" × f² / 2 =
= ("baseline 1" × "height 1" / 2) × f² =
= 45 × f² = 20 cm²
f² = 20/45 = 4/9
f = 2/3
so, for a side of ABC being 3.6cm long, that means the corresponding side in DEF is
3.6 × f = 3.6 × 2/3 = 7.2/3 = 2.4cm
