Question

For which of the following would similar triangles and trigonometry be useful for measuring?
A. The length of a table.
B. The width of a wide river.
C. The length of a car.
D. The width of the classroom.

Answer 1

the length of a table, the width of a classroom, and the length of a car can be easily measured without using trigonometry (could probably use a meter stick or measuring tape) because we can easily reach both ends

the width of a wide river is a little different, it may not be practical to measure the distance across directly.

Answer 2

(just giving an example here)

if we want to measure to the distance across the river, we could stand at A, find an object of reference B, then walk to the right to C such that angle C is 45 degrees. we can then measure the distance from A to C, and using trigonometry, we know that AC and AB are equal, thus giving us the length of the river