The mean of 20 numbers is 15. If each number is multiplied by 3 and then 4 is added, find the new mean.

★★★★☆ (4/5) It loses one star only because it is not a comprehensive academic resource; it is a coaching tool. For the specific purpose of cracking government exams, it is top-tier.

Shahid Jamal is widely respected in the competitive exam circuit for his ability to simplify complex mathematical concepts.