# This is a logical one. If 1=5, 2=10, 3=20, 4=40, then 5=?. This is very simple. If You know the answer, please answer. Hint: Life is very simple, Don't complicate it.

lemjay | Certified Educator

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If 1=5, 2=10, 3=20, 4=40 , then we have a geometric series which is:

`5, 10, 20 , 40, ....`

And its common ratio is:

`r =10/5=20/10=40/20 = 2`

Using the formula,

`a_n=a_1r^(n-1)`

the fifth term is:

`a_5=5*2^(5-1)=5*2^4=5*16=80`

Hence, 5 = 80.

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