4.Which is the best buy in the following cases. b) 5kg of rice for Rs 120 or 9kg of rice for Rs 198

I’m having a hard time understanding your question

Use pythagorean’s theorem and find the missing side lengths of the two smaller triangles and add them together
13^2 - 12^2 = 5
15^2 - 12^2 = 9
5+9 = 14
14 is the length of each side of the square
14^2 + 14^2 = 19.8
19.8 is the diagonal length of the inside if the square