Explanation:

To find the length of the other parallel side of the trapezium:

- The area (A) of a trapezium is calculated using the formula:

$$ A = \frac{1}{2} \times (b_1 + b_2) \times h $$

where \( b_1 \) and \( b_2 \) are the lengths of the parallel sides, and \( h \) is the distance between them.

- Given:

- Area = 1785 sq ft

- Height (h) = 35 ft

- One parallel side (\( b_1 \)) = 42 ft

- Substitute the values into the formula:

$$ 1785 = \frac{1}{2} \times (42 + b_2) \times 35 $$

$$ 1785 = 17.5 \times (42 + b_2) $$

$$ 42 + b_2 = \frac{1785}{17.5} $$

$$ 42 + b_2 = 102 $$

$$ b_2 = 102 - 42 $$

$$ b_2 = 60 $$

- The length of the other parallel side is 60 feet.