Krishna
0

Step 1:  Understand the question and note down the given data

Step 2: Prove that the two triangles are similar by using the given data.

EXPLANATION: From the figure we get

\angle B = \angle Q = 90 \degree

\angle C = \angle R

Because, AC || PR, all sun’s rays are parallel at any instance)

So,  ∆ABC ~ ∆PQR ( by AAA Theorem)

Step 3: Use the AAA theorem to calculate unknown value

AAA THEOREM: In two triangles, if the angles are equal, then the sides

opposite to the equal angles are in the same ratio (or proportional) and hence

the two triangles are similar.

\frac{AB}{PQ} = \frac{BC}{QR}

Step 4: Substitute the known values in the AAA theorem

EXAMPLE:   \frac{1.65}{PQ} = \frac{1.8}{5.4}

PQ = \frac{5.4 * 1.65}{1.8}

PQ = 4.95 m

The height of the lamp post is 4.95 m