SSC CGL (Prelims) General: Arithmetic Progression questions with solutions

Q1. The radii of three concentric circles are in arithmetic progression. If the innermost radius is 7 cm and the outermost radius is 21 cm, what is the radius of the middle circle?

1. 12 cm
2. 11 cm
3. 10 cm
4. 14 cm

Answer: 14 cm

Since the three radii are in arithmetic progression, the middle radius is the average of the first and third radii. So, \((7+21)/2 = 14\) cm.