If y varies directly as x and as the square of z, and y =25/9 when x=5 and z=1, find y when x =1 and z=4

y= 80/9

Step-by-step explanation:

Given

" y varies directly as x" and "as the square of z" so y = x* z²* some number

if y =25/9 when x= 5, z= 1 and y = x*z²* some number

then 25/9  = 5 * 1² * some number

      5*(5/9) = 5 * some number

therefore y = x* z²* (5/9)

y= ? when x=1 , z= 4

y = x * z² * (5/9)

y = 1 * 4² * (5/9)

y = 16*5 / 9

y = 80/9