A coaching institute has students in 3 batches – X, Y and Z. In a certain examination, the average marks obtained by these batches are 72, 60 and 50 respectively. The average marks of batches X and Y taken together is 69. If the ratio of the number of students in batches Y and Z is 6 : 7, what is the average score of all the three batches put together? (a) 59 (b) 61.6 (c) 63.5 (d) 64.7 (e) 65
A private tutor admits 10 students, boys or girls, in a batch. The probability that a student admitted in his batch is girl is 0.4, then number of boys in his batch is:
