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2. Calculate the length of QS in each of the following diagrams. Give your answer
correct to two decimal places if necessary.
(a) P (b) (c) 24 cm
P P S
15 cm 13 cm 6 cm
12 cm S 26 cm Q 30 cm

Q R S Q R R
24 cm

How do you solve problems?

LEARNING
Help! STANDARDS
Help! Solve problems involving
the Pythagoras’ theorem.
Where is Pythagoras?
Can the ladder We need his help!
reach the floor
that is on fire?

A fireman climbs up a ladder to save a child who is trapped
on the third floor as shown in the diagram. The third floor
is 6 m high from the horizontal ground. The base of the
ladder is 4.5 m away from the wall of the building. How long
is the ladder?

Understanding Devising a plan Implementing Doing reflection
the problem • Draw a the strategy 7.5 = 56.25
2
2
2
• Distance of the right-angled R 4.5 + 6 = 56.25
third floor from triangle PQR
the horizontal to represent 6 m
ground = 6 m the given P Q
• Distance of information. 4.5 m
the base of the • Use PR = PQ + QR
2
2
2
ladder from the = 4.5 + 6
2
CHAPTER
2
13 Pythagoras’
building = 4.5 m = 20.25 + 36
• Find the length theorem. = 56.25
of the ladder. PR = 7.5 m
Thus, the length of
the ladder is 7.5 m.
298
Chapter 13

13 TB Math F1.indd 298 11/10/16 12:22 PM