Source: 1992 National High School Mathematics League, Exam One, Problem 3
February 26, 2020
geometry3D geometrytetrahedron
Problem Statement
Areas of four surfaces of a tetrahedron are S1,S2,S3,S4. And the largest one of them is S. λ=SS1+S2+S3+S4, then λ always satisfies
(A)2<λ≤4(B)3<λ<4(C)2.5<λ≤4.5(D)3.5<λ<5.5