No rounding is necessary to answer the question.
We can subtract the (linear) density of the second box from that of the first to see which box is heavier per unit height.

This value is obviously less than zero, so ...
... the box of magazines has the greater mass per unit height.
_____
The question didn't ask for the mass per height, and we didn't compute it. All we did was make a conversion to comparable units. The units we ended up with are mixed English and metric units, but that doesn't matter for the purpose of comparison.
Since all we're really interested in is <em>the sign of the difference</em> of mass/height, we don't even need to actually compute that difference. We just need to do enough computation to be able to tell whether the sign is positive or negative.
Wait what grade is this in also what class is this
Solving for the polynomial function of least degree with
integral coefficients whose zeros are -5, 3i
We have:
x = -5
Then x + 5 = 0
Therefore one of the factors of the polynomial function is
(x + 5)
Also, we have:
x = 3i
Which can be rewritten as:
x = Sqrt(-9)
Square both sides of the equation:
x^2 = -9
x^2 + 9 = 0
Therefore one of the factors of the polynomial function is (x^2
+ 9)
The polynomial function has factors: (x + 5)(x^2 + 9)
= x(x^2 + 9) + 5(x^2 + 9)
= x^3 + 9x + 5x^2 = 45
Therefore, x^3 + 5x^2 + 9x – 45 = 0
f(x) = x^3 + 5x^2 + 9x – 45
The polynomial function of least degree with integral coefficients
that has the given zeros, -5, 3i is f(x) = x^3 + 5x^2 + 9x – 45