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Find the value of l in the frustrum above

Question 1 Report

Find the value of l in the frustrum above

5cm

6cm

7cm

8cm

Answer Details

ΔABE and ΔACD are similar

∴

x

=	3
	6

x+4

6x = 3(x+4)
6x = 3x + 12
3x = 12
x = 4
In ΔACD; L2 = (4+4)2 + 62
= 82 + 62
= 64 + 36
= 100
L =
√ 100
= 10cm
In ABE, AE2 = 42 + 32
= 16 + 9
= 25
AE = 5cm
∴L = 10 - 5
= 5cm

Read lesson note on Mensuration (JAMB)

Mensuration

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