What is the circumference of a circle with diameter 14? (Use π ≈ 22/7)

Circumference = πd = (22/7) × 14 = (22 × 14)/7 = 22 × 2 = 44 units. Or use 2πr with radius = 7: C = 2π(7) = 14π = 14 × (22/7) = 44. Circle formulas: (1) Diameter = 2 × radius, so radius = diameter/2; (2) Circumference C = πd = 2πr (length around the circle); (3) Area = πr² (surface inside); (4) The number π ≈ 3.14159 ≈ 22/7 (rough approximation). The 22/7 approximation works exactly when the radius or diameter is a multiple of 7. The ASVAB sometimes uses 22/7 to enable clean arithmetic without a calculator. For circles where π must remain symbolic, express answers in terms of π: a circle with radius 5 has C = 10π and A = 25π. The relationship C = πd is the geometric definition of π: π is the ratio of any circle's circumference to its diameter — always constant regardless of circle size.