Given:
s is inversely proportional to t.
When s = 0.5, t = 7.
To find:
The value of s when t=0.8.
Solution:
s is inversely proportional to t.

...(i)
Where, k is the constant of proportionality.
Putting s=0.5 and t=7, we get



Putting k=3.5 in (i), we get

This is the equation of proportionality.
Putting t=0.8, we get


Therefore, the value of s is 4.375 when t=0.8.