A prime problem..#3

Number Theory Level 2

Find the next number in the series..

23,21,24,19,26,15,28,11__


The answer is 30.

Mehul Arora by Mehul Arora , 20, India

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2 solutions

Mehul Arora
Jan 8, 2015

The series goes as such..

-2,+3,-5,+7,-11,+13,-17.

Hence the next number will be 30 as 11+19.

We add 19 as the series is alternating with signs and with prime numbers.

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Vishal S
Jan 9, 2015

Since the difference between

23 & 21 is |2|

21 & 24 is |-3|

24 & 19 is |5|

19 & 26 is |-7|

26 & 15 is |11|

15 & 28 is |-13|

28 and 11 is |17|

Since the difference between the magnitude the number is prime number

Therefore the next number in the series is 11+19= 30 \boxed{30}

1 Helpful 0 Interesting 0 Brilliant 0 Confused

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