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The figure below shows a right angled triangle LMN in which LM=7.5cm and LN = 19.5 cm. what is the area of triangle LMN in square centimetres?

Class: KCPE

Subject: Mathematics

Topic: Length,perimeter and area

Lesson Summary

The figure below shows a right angled triangle LMN in which LM=7.5cm and LN = 19.5 cm. what is the area of triangle LMN in square centimetres?

q922320191136.png

A.18
B.67.5
C.27
D.34.5



Text Answer


Apply Pythagoras relation in triangle LMN.

LN²=LM² + NM²

NM²=LN² – LM²

= 19.5²-7.5² = 380.25 – 56.25= 324

NM =√=18𝑐𝑚

Area of triangle LMN =12𝑏𝑎𝑠𝑒×ℎ𝑒𝑖𝑔ℎ𝑡

12×18×7.5= 67.5 cm²

The correct answer is B (67.5).


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