Similar Triangles Similar triangles are very useful for indirectly determining the sizes of items which are difficult to measure by hand.

Typical examples include building heights

Tree Heights

Towers

Similar Triangles can also be used to measure the width of a river.

4. Two instructors want to set up a Flying Fox across a river for an outdoor education camp. achal_pradesh

The first thing they need to know is how wide the river is so they can set up ropes long enough to make the crossing.

Would it be helpful for each person to move further along the river and measure exactly how far they moved from their starting points at A and B?

The lady walks 15 m to the left, and then 5 m back from the river bank to finish at point E.

We can draw in the line of sight from the lady at “E” to the guy on the other side of the river at “C” which then produces a pair of Similar Triangles.

We can solve these “bow tie” triangles and work out the width of the river as shown below.

About how long is the log that goes across the creeks?

Find the distance from the park to the house.