Q. Concrete mixer are generally designed to run at a speed of ……….. Revolution per minute. (A) 40 to 50 (B) 30 to 40 (C) 15 to 20 (D) 20 to 30 👁️ Show Answer 💬 Discuss 🔗 Share ⚡Menu ✅ Correct Answer: (C) 15 to 20