Then y=x(60-x)

(0≤x≤60, and x is an integer)

∴y=-x2+60x

=-(x-30)2+900

∫ The number of quadratic terms-1 < 0, when x=30, it satisfies 0≤x≤60.

When every toy makes a profit in 30 yuan, toys sold for one day make the biggest profit.