Rule of Sum and Rule of Product

Rule of Sum and Rule of Product: Level 2 Challenges


When we write the integers from 1 to 100, how many times does the digit 9 appear?

Which of the following expresses the correct formula for the number of unit squares with exactly 1 red side in an n×n n \times n square with n2 n \geq 2 ?

Find the number of 22 digit numbers whose digit sum is a perfect square.

If you take a 3×3×33 \times 3 \times 3 Rubik cube and break it up into the 33 3^3 cubes, how many cubes would have stickers on exactly 22 faces?

Bonus question: Can you generalize this for a N×N×NN \times N \times N Rubik cube?


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