Challenger: the mass ratio of cement, sand and stone of a kind of concrete is 2:3:5. How many tons of cement, sand and stone are needed to prepare 20 tons of concrete?

Challenger: the mass ratio of cement, sand and stone of a kind of concrete is 2:3:5. How many tons of cement, sand and stone are needed to prepare 20 tons of concrete?

Total shares: 2 + 3 + 5 = 10 (shares), tons of cement: 20 × 210 = 4 (tons), tons of sand: 20 × 310 = 6 (tons), tons of stone: 20 × 510 = 10 (tons); answer: 4 tons of cement, 6 tons of sand, 10 tons of stone are required