Base on the similarity principle of triangles, the distance d across the lake as shown is 90 ft.
Similar triangle theorems
Two triangles are similar if they are only difference in size but have the same shape.
In similar triangles, corresponding sides are always in the same ratio.
Therefore, let's create a proportion from the triangles since they are similar.
40 / d = 20 / 45
cross multiply
45 × 40 = 20d
1800 = 20d
divide both sides by 20
1800 / 20 = 20d / 20
d = 90 ft
learn more on similar triangles here: https://brainly.com/question/25882965
