Final answer:
After coloring at least 6 squares red and ensuring that 7/10 of the grid is colored, the student can use the remaining colors (black, green, and blue) to color 64 squares.
Step-by-step explanation:
The question asks to use a hundredth grid to create a design and adhere to specific rules regarding the number of squares to be colored and the colors to be used. There is a grid with 100 squares (hence the term hundredth grid), and the student must color at least 70 of these squares (7/10) to follow the instructions. Since at least 6 squares must be red, we can calculate the number of squares that can be colored with the remaining colors by subtracting 6 from 70, which leaves us with 64 squares to be colored with black, green, and blue.
To solve this problem, we need to determine how many squares can be colored with the remaining colors, given that we must color at least 7/10 of the squares and use red for at least 6 squares. Let's assume that we color 7/10 of the squares, which is 70 squares out of 100. Since we must use red for at least 6 squares, we subtract 6 from the 70 to get 64 squares colored with the remaining colors. Therefore, the answer is 64 squares.