Average marks boys=52 girls=42 overall=50. Percentage of boys?

In a group of 50 students, average score is 70. Average of 30 boys is 75. Find average of 20 girls.

Average weight of A, B and C is 50 kg. Average of A and B is 55 kg and average of B and C is 43 kg. Weight of B is

The average marks of 13 papers are 40. Average of first 7 is 42 and last 7 is 35. Marks obtained in the 7th paper are

If x is the average of 1², 2², 3², ..., 10² and y is the average of first 10 even natural numbers, then y is what percent of x − y?

Five years ago, the average age of X₁, X₂, X₃ and X₄ was 50 years. If we include X₅, the present average age of all five is 56 years. Then the present age of X₅ is