Question
The average number of books on history, polity and geography in a library is 190, and the average number of books on history and geography is 160. If the number books on geography is 20% less than the number of books on polity, then what is the number of books on history in the library?
Solution
Let the number of books on History, Polity and Geography be x, y and z respectively. Given, (x + y + z)/3 = 190 Or, x + y + z = 570 ….. (1) And, (x + z)/2 = 160 Or, x + z = 320 ….. (2) From equation 1 and 2 Number of books on polity = y = 250 Number of books on geography = 0.8 × 250 = 200 Therefore, number of books on history = 570 – (250 + 200) = 120
More Average Questions
- If average of first 12 numbers is (n – 23) and the sum of remaining number is 925. Find the value of ‘n’, if the average of 22 numbers is ‘n’.
- The mean of 15 observations is 124 and the median of the observations is 130. Find the mode of the observations.
- The average weight of 30 students in a class is 60 kg. When one student leaves and another joins, the average becomes 59.5 kg. The student who left had wei...
- The average monthly fee for 30 students in a workshop is Rs. 10,000. After an increase, the new monthly average fee for each student is Rs. (10000 + X). If...
- The earnings of ‘U’, ‘V’, and ‘W’ are in the ratio 2:3:5. Their average income is Rs. 18,000. If they spend 45%, 55%, and 65% of their respective incomes, ...
- The mean weight of 'w' students in a classroom is 42 kg. When the class teacher, weighing 61.5 kg, is added to the group, the average weight increases by 0...
- The average of two consecutive even numbers is 81. If the smaller number is increased by 15% and the larger number is decreased by 15%, then find the diffe...
- The average run rate of a cricket team during the first 20 over’s is 4.5. What should be the asking rate per over for the next 30 over’s. if it has to chas...
- There are 4 numbers – A, B, C & D. B is 25% more than A and D is equal to average of A & C. Ratio of A to C is 3 : 4 and C is 5 more than B. Find value of ...
- Fifteen numbers have an average of 70. The average of the first seven is 60, and the average of the last five is 63. The eighth number is 50% of the ninth,...
Relevant for Exams:
