A series is given with one number missing. Choose the number that will complete the series. 7, 21, 63, ?, 567, 1701

Question

A series is given with one number missing. Choose the number that will complete the series. 7, 21, 63, ?, 567, 1701

1. A. 189 (Correct answer)
2. B. 136
3. C. 111
4. D. 191

Correct Answer

Option A — 189

Detailed Solution & Explanation

The correct answer is 189.

Key Points

• This is a geometric progression where each term is obtained by multiplying the previous one by a constant ratio.
• Series: 7, 21, 63, ?, 567, 1701
• 7 × 3 = 21
• 21 × 3 = 63
• 63 × 3 = 189
• 189 × 3 = 567 ✓
• 567 × 3 = 1701 ✓
• The common ratio is 3, so the missing term is 63 × 3 = 189, which also correctly gives 567 when multiplied by 3.
• in a geometric progression (GP), consecutive terms share a constant ratio (here 3), unlike an arithmetic progression which has a constant difference.
• Divide any term by the one before it to find the ratio.

Exam Tip

• the two terms after the blank (567, 1701) let you confirm the ratio independently — a reliable way to check your answer fits from both sides.