MIT 6.042J: Mathematics for Computer Science
6.042J, now numbered 6.1200J, is MIT's discrete math course for CS: proofs, induction, number theory, graph theory, counting, and discrete probability. Its OCW versions, with full lecture videos and the famous free textbook, make it one of the most-used discrete math resources in the world.
Fennie is independent and not affiliated with MIT. This is an unofficial study guide.
What makes it hard
It's most students' first real proof-writing course, and the standard for rigor is high: induction proofs with imprecise inductive hypotheses get shredded. The probability unit at the end is deceptively hard, and self-learners often skip the exercises that build the actual skill.
What you'll cover
- • Proof techniques and induction
- • Number theory
- • Graph theory
- • Counting and combinatorics
- • Recurrences
- • Discrete probability
The 6.042J study guide
How to study for MIT 6.042J, step by step.
- 1
Read the free textbook alongside the lectures
Mathematics for Computer Science by Lehman, Leighton, and Meyer is free through OCW and aligned to the course. The lectures motivate; the book's precision is what the graded standard of rigor actually demands.
- 2
Write proofs daily, starting small
Proof-writing compounds with frequency, not session length. One careful induction or contradiction proof per day, audited against a solution, builds the skill faster than weekend marathons.
- 3
Do all the in-text exercises
Self-learners on OCW most often skip the exercises embedded in the readings, which is where the actual skill gets built. Treat them as mandatory, and check posted solutions only after attempting.
- 4
Budget extra time for counting and probability
The combinatorics and discrete probability units are deceptively hard; confidence outruns competence here more than anywhere in 6.042. Double your usual practice volume for these weeks.
Today
Today's 6.042J plan
What a Fennie Daily Plan looks like for 6.042J. Yours is built from your own syllabus and adapts every day to your deadlines and progress.
First plan free, no card required. Fennie is independent and unaffiliated with your school.
FAQ
Is 6.042 hard?
It's a real step up if you've never written proofs: rigor is graded, not just answers. Students who write proofs daily and get feedback adapt within weeks.
Should I take 6.042 before 6.006?
Yes, that's the designed order. 6.006 leans on the proof and graph-theory fluency 6.042 builds. Self-learners should follow the same sequence.
Is the 6.042 textbook really free?
Yes. Mathematics for Computer Science by Lehman, Leighton, and Meyer is freely available through OCW, with readings, problems, and lecture videos aligned to it.
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