Question

z varies inversely with the product of x and y. when x=2 and y=4, z=0.5. what is the value of z when x=4 and y=9? please help, i've tried different things and i can't seem to get the correct answer. my choices are a: 45/2 b: 40/9 c:40 d: 1/9

Answer 1

If z varies inversely with the product of x and y:
z = k/ (x*y)
0.5 = k/(2*4)
0.5 = k/ 8
k = 0.5 * 8
k = 4.
Therefore, when x = 4 and y = 9:
z = 4 / (4*9) = 4/36 = 1/9
Answer: D ) 1/9