Maths Olympiad Prep

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Problem 316

Geometry Difficulty 1.9 Find the answer CEMC Pascal

In rectangle PQRSPQRS, PS=6PS=6 and SR=3SR=3. Point UU is on QRQR with QU=2QU=2. Point TT is on PSPS with TUR=90\angle TUR=90^{\circ}. What is the length of TRTR?

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

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Official solution

Since PQRSPQRS is a rectangle, then QR=PS=6QR=PS=6. Therefore, UR=QRQU=62=4UR=QR-QU=6-2=4. Since PQRSPQRS is a rectangle and TUTU is perpendicular to QRQR, then TUTU is parallel to and equal to SRSR, so TU=3TU=3. By the Pythagorean Theorem, since TR>0TR>0, then TR=TU2+UR2=32+42=25=5TR=\sqrt{TU^{2}+UR^{2}}=\sqrt{3^{2}+4^{2}}=\sqrt{25}=5. Thus, TR=5TR=5.

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