logic question

Question

what is the missing no in following series

500,1800,100, _ , 20,50,4 explain with logic

Answer 1

300

 

500/5=100

100/5=20

20/5=4

 

 

And  1800/6=300

300/6=50

Comments

how did you guess that 1800 will be divided by 6?

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Actually we are getting third term by dividing first term by 5....fifth term by dividing third term by 5.....so there must be some pattern between second....fourth  .sixth term.....
Let we are dividing by x. Then  fourth term is 1800/x. And sixth term is (1800/x)/x=50

So x=6

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correction:-

the third term should be $\frac{1800}{x}$

the fifth term should be $\frac{\frac{1800}{x}}{x}$ = $\frac{1800}{x^{2}}$

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Yes.....now i have corrected