The area of a rhombus is 110 cm 2 . If the diagonals are 20
MATHEMATICS
WAEC 2015
The area of a rhombus is 110 cm2. If the diagonals are 20 cm and (2x + 1) cm long, find the value of x.
- A. 5.0
- B. 4.0
- C. 3.0
- D. 2.5
Correct Answer: A. 5.0
Explanation
Diagonal |AC| = (2x + 1)cm
In the diagram,area of \(\Delta\)ABC
is \(\frac{110}{2}\) = \(\frac{1}{2}\) x |AC| x |HB|
55 = \(\frac{1}{2}\) x (2x + 1) x 10
55 = (2x + 1)5
55 = 10x + 5
55 - 5 = 10x
50 = 10x
x = \(\frac{50}{10}\)
= 5.0
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