Step 1: Investigate the given question and write the given values

NOTE: The two triangles are similar

EXAMPLE: ∆ABC ~ ∆PQR

Perimeter of △ABC = 20 cm.

Perimeter of △PQR = 30 cm.

One side of the first triangle QR = 12 cm, BC = ?

Step 2: Utilize the similarity principle to solve this

NOTE: If two triangles are similar then ratio of the perimeters of the

triangles is equal to the ratio of their corresponding sides.

\frac{perimeter of ABC}{perimeter of PQR} = \frac{BC}{QR}

Step 3: Substitute the known values and simplify

EXAMPLE: \frac{20}{30} = \frac{BC}{12}

\frac{20 * 12}{30} = BC

BC = 8 cm

So required value of the corresponding side is 8 cm