Jorge Fernández-Hidalgo

 154 If nine coins are tossed, what is the probability that the number of heads is even? 55 Multiple-choice: sum of primes below $1000$ 54 Without using a calculator and logarithm, which of $100^{101} , 101^{100}$ is greater? 49 Research done by high-school students 46 You have to estimate $\binom{63}{19}$ in $2$ minutes to save your life.

### Reputation (89,901)

 +10 Definition of notation $\mathbb Z_n$ +10 Counting with restrictions. +10 Finding a separating family of subsets of $[n]$ of size $n+1$. +10 Show that every group of prime order is cyclic

### Questions (328)

 118 Examples of problems that are easier in the infinite case than in the finite case. 116 What is category theory useful for? 89 What are the differences between class, set, family, and collection? 66 What's a good place to learn Lie groups? 40 Joke explanation: “a comathematician is a device for turning cotheorems into ffee”

### Tags (455)

 1k combinatorics × 635 452 number-theory × 206 777 elementary-number-theory × 333 444 graph-theory × 278 695 abstract-algebra × 320 406 probability × 176 606 group-theory × 271 375 algebra-precalculus × 108 510 discrete-mathematics × 192 310 real-analysis × 169

### Bookmarks (183)

 779 How to study math to really understand it and have a healthy lifestyle with free time? [closed] 416 Proofs that every mathematician should know. [closed] 287 Nice examples of groups which are not obviously groups 244 Fun but serious mathematics books to gift advanced undergraduates. 183 What were some major mathematical breakthroughs in 2016? [closed]