If x, y, z are three sum of money such that y is the simple interest on x and z is the simple interest on y for the same time and at the same rate of interest, then what is the relation between x, y, z we have = ?
A
x<sup>2</sup> = xy
B
xyz = 1
C
x<sup>2</sup> = yz
D
y<sup>2</sup> = zx
Correct Answer: y<sup>2</sup> = zx
Let the time is 't' years and the rate of interest is R%According to the question,
$$\eqalign{ & {\bf{Case(I):}} \cr & y = \frac{{x \times {\text{R}} \times {\text{t}}}}{{100}}.....(i) \cr & {\bf{Case(II):}} \cr & z = \frac{{y \times {\text{R}} \times {\text{t}}}}{{100}}.....(ii) \cr} $$
By dividing equation (i) by equation (ii)
$$\eqalign{ & \frac{y}{z} = \frac{{x \times {\text{R}} \times {\text{t}}}}{{y \times {\text{R}} \times {\text{t}}}} \cr & \Rightarrow {y^2} = zx \cr} $$
