Multiple choice

A series is given with one term missing. Choose the correct alternative from the given ones that will complete the series. 21567, 20726, 20150, 19789, 19593, ?

  1. 19452

  2. 19512

  3. 19493

  4. 19502
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The series is 21567, 20726, 20150, 19789, 19593, ?. The differences are: 21567-20726=841, 20726-20150=576, 20150-19789=361, 19789-19593=196. These differences are: 841=29², 576=24², 361=19², 196=14². The bases decrease by 5 each time (29, 24, 19, 14). The next base should be 9, so the next difference is 9²=81. Therefore: 19593 - 81 = 19512.

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