91Ó°ÊÓ

Area A of a triangle having base b and height h is

$A=\frac{1}{2}×b×h$

Substitute 4 for b and 10 for h in this equation to get area of given triangle

$\begin{array}{l}A=\frac{1}{2}×4×10\\ A=20\text{sq.ft}\end{array}$

Area A of a rectangle having width w and lengthl is

$A=wl$$A=wl$

Substitute$1.6\text{ft}$for w and$25\text{ft}$for l in the equation of area of rectangle

$\begin{array}{c}A=1.6×25\\ A=40\text{sq.ft}\end{array}$

Since, Area of rectangle is not equal to area of triangle

Thus, option (A) is incorrect

Substitute$5\text{ft}$ for w and$16\text{ft}$ for l in the equation of area of rectangle

$\begin{array}{c}A=5×16\\ A=80\text{sq.ft}\end{array}$

Since, Area of rectangle is not equal to area of triangle

Thus, option (B) is incorrect

Substitute$3.5\text{ft}$ for w and$4\text{ft}$ for l in the equation of area of rectangle

$\begin{array}{c}A=3.5×4\\ A=14\text{sq.ft}\end{array}$

Since, Area of rectangle is not equal to area of triangle

Thus, option (C) is incorrect

Substitute$0.4\text{ft}$ for w and$50\text{ft}$ for l in the equation of area of rectangle

$\begin{array}{c}A=0.4×50\\ A=20\text{sq.ft}\end{array}$

Since, Area of rectangle is equal to area of triangle

Thus, option (D) is correct.

Hence, correct option is (D).