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**1. The problem statement, all variables and given/known data**

A body is dropped from certain height H. If the ratio of the distances travelled by it in (n-3) seconds to (n-3)rd second is 4:3, find H (take g= 10 m/s²) (answer: 125m)

**2. Relevant equations**

**3. The attempt at a solution**

I did this way but I came to a dead end...

To find H,

s= 1/2 gt²

= 1/2 * 10 * (n-3)²

= 5*(n²-9)

= 5n²+45.......(I)

S nth = u+g/2(2n-1)

= 5(2n-1)

= 10n-5.....(II)

equating (I) AND (2)

5n²+45= 4

________ ___

10n-5. 3

=> 3(5n²+45)=4(10n-5)

=> 15n²+135=40n-20

=> 15n²-40n=-20-135

=> 15n²-40n=-155

=> 15n²+155=40n

=> 15n²+155= 40

____________

n

This is a dead end....what should I do next...???