Here are some problems I've come up and their corresponding solutions sorted by topic.

Modular Arithmetic

• Check Your Exponents

RSA Encryption

• That Looks Familiar
• Does this work?

Counting

• A Little Game

Intro to Probability

• Enveloped Intervals

Random Variables

• Ber-who?-lli

Expectation and Variance

• Jensen's Polynomials

Covariance and Correlation

• To be XOR not to be

Markov Chains

• Riemann's Pontiac