The perimeter of a rhombus is 100 cm. One of the diagonal is 30 cm. What is the length (in cm) of the other diagonal?
Show answer & explanation
Correct answer: A
Explanation
Side of the rhombus = 100 / 4
= 25 cm
Half of the first diagonal = 30 / 2
= 15 cm
Let half of the second diagonal = x cm
By Pythagoras theorem,
25² = 15² + x²
625 = 225 + x²
x² = 400
x = 20
Second diagonal = 2 × 20
= 40 cm