Find the number that will come in place of the question mark (?) in the…
2019
Find the number that will come in place of the question mark (?) in the following series. Series : 400, 625, ?, 1225, 1600
Answer: D. 900 — Observe the square roots of the terms: 400 = 20 × 20 = 400 625 = 25 × 25 = 625 ? = 30 × 30 = 900 1225 = 35 × 35 = 1225 1600 = 40 × 40 = 1600 The square roots…
- A.
925
- B.
850
- C.
1000
- D.
900
Attempted by 340 students.
Show answer & explanation
Correct answer: D
Observe the square roots of the terms:
400 = 20 × 20 = 400
625 = 25 × 25 = 625
? = 30 × 30 = 900
1225 = 35 × 35 = 1225
1600 = 40 × 40 = 1600
The square roots form the sequence 20, 25, 30, 35, 40, increasing by 5 each time.
Therefore the missing number is 30 × 30 = 900.
Final answer: 900
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