The ratio of number of boys and girls in a class is 2 : 3. The average weight of boys and girls in the class is 18 kg and 21 kg respectively. What is the average weight (in kgs) of all the boys and girls together?
1. Seven friends spent Rs 14 each on a project and the eighth friend spent Rs 21 more than the average expenditure of all eight of them. What is the amount of total money (in Rs) spent by them?
3. A group of boys has an average weight of 36 kg. One boy weighing 42 kg leaves the group and another boy weighing 30 kg joins the group. If the average now becomes 35.7 kg, then how many boys are there in the group?
4. The average marks in science subject of a class of 20 students is 68. If the marks of two students were misread as 48 and 65 of the actual marks 72 and 61 respectively, then what would be the correct average?
7. Consider the following grouped frequency distribution: x f 0-10 8 10-20 12 20-30 10 30-40 p 40-50 9 If the mean of the above data is 25.2, then what is the value of p?
Median = mid value = average of 21st and 22nd value
Arranging data in increasing order we get
x f
4 6
5 4
6 5
7 4
8 6
9 9
10 8
So mid value i.e 21st and 22nd value = 8
9. The mean of marks secured by 65 students in division A of class X is 54, 30 students of division B is 50 and that of 55 students of division C is 48. Find the mean of marks of the students of three divisions of Class X.
10. Among four students sitting in a row, average age of last three students is 20 years and the average age of first three students is 21 years. If the age of first student is 26 years, then what is the age (in years) of the last student?