Averages
Practice Questions on Averages
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Q19) Expenses at a hostel are partly fixed and partly varying on the number of hostlers. The average expense per hostler is Rs. 700 with 25 hostlers. The average expense per hostler comes to Rs. 600 when the number of hostlers is 50. What will be the average cost per hostler when there are 100 hostlers? 1) 550 2) 560 3) 570 4) 540 Let us suppose F are the fixed expenses and V are the variable expenses per head. Total charges for 25 hostlers are fixed charges + variable charges for 25 hostlers F + 25V = 700×25 ....(1) Similarly, F + 50V = 600×50 ....(2) Solving Eq 1 and Eq 2 F = 5000, V = 500 Hence, for 100 hostlers total charges are given by F + 100V = 5000 + (100×500) = 55000 Total charges for 100 hostlers are Rs. 55000. Hence, average cost per hostler when there are 100 hostlers is Rs. 550 Hence, option 1. Q20) Average age of boys in the class is 15.2 years, whereas average age of the girls in 16.3 years. Average age of the entire class is 16.1 years. Which of the following could be the possible number of students in the class? 1) 27 2) 63 3) 49 4) 55 Let us suppose that there are 'b' boys and 'g' girls in the class. 15.2b + 16.3g = 16.1(b + g) On solving, 0.2g = 0.9b 2g = 9b g/b = 9/2 From the above ratio we can say that, g = 9k and b = 2k Hence, Total number of students = g + b = 9k + 2k = 11k ∴ Total number of students in the class has to be divisible by 11 Hence, option 4. Q21) If 47a + 47b = 5452 what is the average of a and b? 1) 116 2) 96 3) 58 4) 86 47a + 47b = 5452 a + b = 5452/47 =116 Average of a and b = 58 Hence, option 3. Q22) If x + y + z = 13 then the maximum value of (x - 2)(y + 1)(z - 3) is 1) 25 2) 27 3) 9 4) 54 As AP ≥ GP   Maximum value of (x-2)(y+1)(z-3) is 27 Hence, option 2. |