1. The problem statement, all variables and given/known data This is from Advanced Physics by Adams and Allday, section 9.11, question 2 c. What is the quark content of each of the following particles? [snip] c) Λ baryon, strangeness = -1, mass 1.12 GeV/c2? 2. Relevant equations No equations. Table of masses at http://en.wikipedia.org/wiki/List_of_particles. Strangeness of s quark is -1 and anti-s quark is +1 3. The attempt at a solution A baryon, so composed of three qwarks or three anti-quarks. The strangeness of -1 requires an s quark so the other two quarks cannot be anti-quarks. The s quark has mass 104 MeV leaving 1.016 GeV for the other two quarks. I cannot find any combination of quarks that adds up to ~1 GeV. The book lists the answer as uds (all anti-quarks) but an anti-s would have strangeness +1 and the mass of mass of uds is 2.4 MeV + 4.8 MeV + 104 MeV = 111 MeV which is ~ a tenth of the given mass. I must be misunderstanding something fundamental here because I cannot deduce the same answers as the book for any of parts a through d so have picked c as a sample to ask about.