The side of a rhombus is 10cm long, correct to the nearest whole number. Between what limits should the perimeter P lie?

A.
39cm ≤ P ≤41cm 
B.
38cm ≤ P 
C.
38.5 ≤ P ≤ 41.5cm 
D.
38.5 ≤ P ≤ 40cm
Correct Answer: Option B
Explanation
If the side = 10 cm, correct to the nearest whole number, then
The side ranges from 9.5 cm to 10.5 cm. (9.5 (leq) s < 10.5)
Perimeter of a rhombus = 4 x side
(therefore) 4 x 9.5 (leq) perimeter < 4 x 10.5
= 38 cm (leq) P < 42 cm