A problem by Owais Shah

Level 2

F i n d t h e 10 t h n u m b e r i n t h e s e q u e n c e : 0 , 4 , 18 , 48 , 100 , 180 , . . . . . . , 10 t h = ? Find\quad the\quad 10th\quad number\quad in\quad the\quad sequence:\\ 0,\quad 4,\quad 18,\quad 48,\quad 100,\quad 180,......,\quad \boxed { 10th=? }


The answer is 900.

Owais Shah by Owais Shah , 34, United Kingdom

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2 solutions

Roberto Gallotta
Dec 22, 2015

Starting from 4, we know that 4=2x2. 18 can be considered 3x6, but 6=2x3. Each number of the series is (number of the series)x(product of the previous number and the number of the series itself). This way we have: 1) 0 (1x0) 2) 4 (2x2) (where the second 2 is 2x1) 3) 18 (3x6) (where 6 is 3x2) 4) 48 (4x12) (where 12 is 4x3) 5) 100 (5x20) (where 20 is 5x4) 6) 180 (6x30) (where 30 is 6x5) [...] 10) 900 (10x90) (where 90 is 10x9)

2 Helpful 0 Interesting 0 Brilliant 0 Confused
Owais Shah
Dec 22, 2015

0 Helpful 0 Interesting 0 Brilliant 0 Confused

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