What is 5π⁄4 radians in degrees?

- (a)225°
- (b)180°
- (c)240°
- (d)360°
Answer
Why
Correct — A. π radians = 180°, so radians turn into degrees on multiplying by 180°⁄π.
Multiply: 5π⁄4 × 180°⁄π
Cancel π: 5 × 180° ÷ 4
= 900° ÷ 4 = 225° → option (a)
Why the others are wrong
- (b)180° — 180° is π radians. 5π⁄4 is π plus π⁄4, so it lies 45° beyond 180°.
- (c)240° — 240° is 4π⁄3 radians (240 × π⁄180), which is 15° more than 5π⁄4.
- (d)360° — 360° is 2π radians, a full turn. 5π⁄4 is only 1.25π, so it is less than 360°.
Concept
Radians and degrees measure the same angle in different units. A full turn is 2π radians = 360°, so π radians = 180°.
Degrees = radians × 180⁄π, and radians = degrees × π⁄180.
For multiples of π⁄4, each π⁄4 is 45°: 5π⁄4 is five of them, 5 × 45° = 225°, which lies between 180° and 270°.
Key facts
- π radians = 180°, so 1 radian = 180°⁄π ≈ 57.3°.
- π⁄6 = 30°, π⁄4 = 45°, π⁄3 = 60° and π⁄2 = 90°.
- 5π⁄4 = 225°, an angle between 180° and 270°.
Study next
Common traps
- Multiplying by π⁄180 instead of 180⁄π: that is the degrees-to-radians factor, and here it gives 5π²⁄720, not an angle in degrees.
- Taking 5π⁄4 as 5⁄4 of a full turn (360°) instead of 5⁄4 of π (180°), which gives 450°.
The same conversion decides sector comparisons: on 17 Sep 2025, 16:00, Quant Q.17 the first sector has a central angle of 180° and the second one of π⁄2 radians (90°), both of radius 12 cm, so first : second = 2 : 1.
On 18 Sep 2025, 12:30, Quant Q.17 the two angles are 120° and 2π⁄3 radians, which are the same angle, so the ratio is 1 : 1.
Related PYQs
No directly related past PYQ was found.