If in two triangles ABC and PQR, $\frac{\mathrm{AB}}{\mathrm{QR}}=\frac{\mathrm{BC}}{\mathrm{PR}}=\frac{\mathrm{CA}}{\mathrm{PQ}}$, then

Given that, in triangles ABC and PQR, $\frac{\mathrm{AB}}{\mathrm{QR}}=\frac{\mathrm{BC}}{\mathrm{PR}}=\frac{\mathrm{CA}}{\mathrm{PQ}}$.

As we know the SSS similarity criterion states that if in two triangles, corresponding sides are in the same ratio, then their corresponding angles are equal and hence the triangles are similar.

Therefore, ΔABC ~ ΔQRP