Which expression gives the perimeter of a rhombus, given side length a?

Which expression gives the perimeter of a rhombus, given side length a?

• A. P = 4a
• B. P = a^4
• C. P = 2a + 2b
• D. P = 4b

Answer: (A)

A rhombus has four equal sides, so its perimeter is the sum of all four sides. If each side is length a, the perimeter is a + a + a + a = 4a. The other options don’t fit: a^4 isn’t a perimeter sum; 2a + 2b is the perimeter of a shape with two different side lengths (like a rectangle); and 4b would require every side to be b, not a. So the expression is P = 4a.

A rhombus has four equal sides, so its perimeter is the sum of all four sides. If each side is length a, the perimeter is a + a + a + a = 4a. The other options don’t fit: a^4 isn’t a perimeter sum; 2a + 2b is the perimeter of a shape with two different side lengths (like a rectangle); and 4b would require every side to be b, not a. So the expression is P = 4a.