Mathematics

Find the value of l in the frustrum above

Find the value of l in the frustrum above
  • A.
    5cm
  • B.
    6cm
  • C.
    7cm
  • D.
    8cm
Correct Answer: Option A
Explanation

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
= 100L =
 100 

= 10cm
In ABE, AE2 = 42 + 32
= 16 + 9
= 25
AE = 5cm
∴L = 10 – 5
= 5cm