Proportion

Consider the following statements : 1. If x is directly proportional to z and y is directly proportional to z, then (x^(2) - y^(2)) is directly proportional to z^2 . 2. If x is inversely proportional to z and y is inversely proportional to z, then (xy) is inversely proportional to z^2 . Which of the above statements is/are correct?

If the kinetic energy of body is directly proportional to time t , the magnitude of force acting on the body is (i) directly proportional to sqrtt (ii) inversely proportional to sqrtt (iii) directly proportional to the speed of the body. (iv) inversely proportional to the speed of the body.