The diagonals of a rhombus are in the ratio 3 : 4. If the length of each side of the rhombus is 12.5 units, what is the length of the shorter diagonal?
- AOption (a)
15 units
- BOption (b)
20 units
- COption (c)
12 units
- DOption (d)
18 units
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Correct answer
15 units
Why this answer is correct
Shortcut Trick
The ratio of diagonals is 3 : 4, so the ratio of half-diagonals is also 3 : 4.
In a rhombus, half-diagonals and the side form a right-angled triangle.
Using the Pythagorean triplet (3, 4, 5), the side corresponds to ratio 5.
Given side length 5 units → 12.5, so 1 unit → 2.5.
Shorter diagonal ratio is 3 × 2 = 6 units → 6 × 2.5 = 15 units.
∴ The correct answer is 15 units.
Alternate Method
Given:
Ratio of diagonals (d1 : d2) = 3 : 4
Length of each side (a) = 12.5 units
Formula Used:
In a rhombus, the relation between side and diagonals is: a2 = (d1/2)2 + (d2/2)2
Calculations:
⇒ Let the diagonals be d1 = 3x and d2 = 4x.
⇒ (12.5)2 = (3x/2)2 + (4x/2)2
⇒ 156.25 = (1.5x)2 + (2x)2
⇒ 156.25 = 2.25x2 + 4x2
⇒ 156.25 = 6.25x2
⇒ x2 = 156.25 ÷ 6.25 = 25
⇒ x = √25 = 5
⇒ Length of shorter diagonal (d1) = 3 × 5 = 15 units.
∴ The correct answer is 15 units.
Additional Information
Properties of Rhombus Diagonals
The diagonals of a rhombus bisect each other at right angles (90°).
Area of a Rhombus
The area can be calculated using diagonals: Area = 1/2 × d1 × d2.
Perimeter of a Rhombus
Since all sides are equal, the perimeter = 4 × side.