381. The average amount with a group of seven numbers is Rs. 20. If the newly joined member has Rs. 50 with him, what was the average amount with the group before his joining the group?
A. Rs. 25
B. Rs. 18
C. Rs. 15
D. Rs. 22
382. The sum of five numbers is 655. The average of the first two numbers is 85 and the third number is 125. Find the average of the two numbers?
383. Find the average of the series : 312, 162, 132, 142 and 122?
384. The average age of a group of 10 persons was decreased by 3 years when one person, whose age was 42 years, was replaced by a new person. Find the age of the new person?
385. The average of the marks of 12 students in a class is 36. If the marks of each student are doubled, find the new average?
386. The average of 10 numbers is 23. If each number is increased by 4, what will the new average?
387. The average of 35 numbers is 25. If each number is multiplied by 5, find the new average?
388. The average salary of a person for the months of January, February, March and April is Rs.8000 and that for the months February, March, April and May is Rs.8500. If his salary for the month of May is Rs.6500, find his salary for the month of January?
389. The average marks of a class of 30 students is 40 and that of another class of 50 students is 60. Find the average marks of all the students?
390. A salt manufacturing company produced a total of 5000 tonnes of salt in January of a particular year. Starting from February its production increased by 100 tonnes every month over the previous months until the end of the year. Find its average monthly production for that year?