Which term of the progression 0.004,0.02,0.1,… is 12.5.?

Explanation

Given: a = 0.004

r =` t_2/t_1` = `(0.02/0.004) = 5`

` T_n `= 12.5

So, `T_n` = `ar^(n-1)`

` 12.5 = (0.004) (5)^(n-1 )`

`12.5/0.004 = 5^(n-1)`

` 3000 = 5^(n-1)`

` 5^5 = 5^(n-1)`

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