Mathematics

Problem

\triangle ABC

is right-angled at

B

with

AB = 8\,\text{cm}

and

AC = 17\,\text{cm}

\triangle PQR

is right-angled at

Q

with

PQ = 8\,\text{cm}

and

PR = 17\,\text{cm}

. If

BC = 15\,\text{cm}

, find the length of

QR

, giving a reason for your answer.