For which of the following would similar triangles and trigonometry be useful for measuring?

The length of a table.

The width of a wide river.

The length of a car.

The width of the classroom.

To measure the length of a table, the length of a car, or the width of

the classroom, you can walk from one end to the other, and you can

stretch a string or a tape measure the whole distance.

But if you need to measure the width of a river, there's no way to walk

a straight line between the ends of the measurement, and it's almost

impossible to use a ruler or a tape measure. You have to find another,

more clever way to measure it.

A little bit of trigonometry makes the job easy. I'll have to admit, though,

I don't immediately see where similar triangles would have to be involved.