Answer
The wide of a strip he should cultivate is 4ft
Given
A farmer has a 100 ft by 50 ft rectangular field that he wants to increase by 25.28% by cultivating a strip of uniform width around the current field
Solution
Since, the increment is by 25.28%

We cross multiply and solve for w
![\begin{gathered} ((100+2w)(50+2w)-100(50))/(100(50))=0.2528 \\ \\ ((100+2w)(50+2w)-100(50))/(5000)=0.2528 \\ \text{Cross multiply} \\ (100+2w)(50+2w)-100(50)=0.2528*5000 \\ (100+2w)(50+2w)-5000=0.2528*5000 \\ \text{open the bracket} \\ 5000+200w+100w+4w^2-5000=1264 \\ collect\text{ like terms } \\ 200w+100w+4w^2-5000+5000=1264 \\ 300w+4w^2=1264 \\ 4w^2+300w-1264=0 \\ \text{Divide all through by 4} \\ w^2+75w-316=0 \\ \end{gathered}]()
We can now solve the quadratic equation by factorisation

Distance can't be negative
Therefore, the wide of a strip he should cultivate is 4ft