(iii) 
Let 
……….(i)
= 
……….(ii)
Now, from eq. (i), 
= 
Here, 
and 
, then
= 
Since, 
and 
is approximately equal to 
and 
respectively.
From eq. (ii), 
= 
Therefore, approximately value of is 0.8 – 0.025 = 0.775.
(iv) 
Let 
……….(i)
= 
……….(ii)
Now, from eq. (i),
= 
Here, 
and 
,
then
= 
Since, and is approximately equal to and respectively.
From eq. (ii), 
= 
= 0.0083
Therefore, approximately value of is 0.2 + 0.0083 = 0.2083.