Percentage of black T-shirt sold = 320/400 x 100 = 80%
Percentage of blue T-shirt sold = 270/300 x 100 = 90%
Answer: There is a greater percentage of Blue T-Shirt sold.
First off, let's change the format of the percentage to decimal.. so 35% is just 35/100 or 0.35 and 40% is 40/100 or 0.4 and so on.

now, whatever "x" amount is, we know that x + 10 must add up to "y". x + 10 = y, because both quantities added will give the mixture amount.
and whatever 0.35x + 4 = 0.37y, because both concentrated amounts must give the 37% of the mixture.

solve for "x", to see how much of the 35% solution will be needed.
what about "y"? well, x + 10 = y.
Answer: he will need 355.68 centimeters³ of sand to fill half of the sandbox
Step-by-step explanation:
The formula for determining the volume of a rectangular prism is expressed as
Volume = length × base × height
It can also be expressed as
Volume = base area × height
The area of the base of the sandbox is 124.8 square centimeters, and it will have a height of 5.7 centimeters. This means that the volume of the sandbox is
124.8 × 5.7 = 711.36 centimeters³
Since Mr. Berger plans to fill the sandbox half full of sand, the volume of sand he will need to fill half of the sandbox is
711.36/2 = 355.68 centimeters³