Answer: (b)-175 ft
Step-by-step explanation:
In [tex]\triangle ABC\ \text{and}\ \triangle CDE[/tex]
[tex]\angle ACB=\angle ECD\quad [\text{vertically opposite angles}]\\\angle ABC=\angle CDE\quad [\text{Each angle is }90^{\circ}]\\\therefore \triangle ABC \sim\ \triangle CDE\quad [\text{by AA similarity criteria}][/tex]
(ii)for similar triangles, we can write
[tex]\Rightarrow \dfrac{100}{d}=\dfrac{4x}{7x}\\\\\Rightarrow d=100\times \dfrac{7}{4}=175\ ft[/tex]
