Averages
Practice Questions on Averages
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Q1) A student appears in 5 papers each of maximum marks 100, and his score in four papers is 62, 87, 79, 53. He does not know his score in the fifth paper, but he knows that his average marks are 74. So how much did he score in the fifth paper ? 1) 79 2) 92 3) 83 4) 89 Let y be his score in the fifth paper  On solving, y = 89 Hence, option 4. Q2) 9 friends went to a hotel for having snacks. Eight of them spent Rs 16 each and the ninth spent Rs 12 more than the average expenditure of all the nine. What was the average expenditure? 1) 16.5 2) 28 3) 21 4) 17.5 Let the average expenditure be y. A.T.Q. 8 × 16 + (y + 12) = 9y; 8y = 140; y = 17.5 Hence, option 4. Q3) Of the three numbers, first is twice the second and thrice the third. If the average of the three numbers is 22, find the largest number. 1) 36 2) 24 3) 18 4) None of these Let first number be x, second be x/2 and third be x/3  x = 36 Hence, option 1. Q4) Average of 10 numbers is zero. Of them, at the most, how many can be less than zero? 1) 0 2) 9 3) 1 4) 10 If average of 10 numbers is zero then this means that some of the numbers are greater than 0 and some of them are less than 0. In this case at most 9 numbers can be less than zero and there isat least one number which is more than 0. Hence, option 2. Q5) What is the average of 5 consecutive even numbers (a, b, c, d, e)? 1) a + 4 2) (a + 4)/5 3) (2a + 8)/5 4) c/5 a, b = a + 2, c = a + 4, d = a + 6, e = a + 8 Average  Hence, option 1. Q6) The average age of 30 girls is 13 yr. The average of first 18 girls is 15 yr. Find out the average age of remaining 12 girls. 1) 12 yr 2) 10 yr 3) 16 yr 4) 10.5 yr Total age of 30 girls = 30×13 = 390 yr Total age of 18 girls = 18×15 = 270 yr Age of remaining 12 girls = 390 – 270 = 120 yr Required average = 120/12 = 10 yr Hence, option 2. Q7) The average weight of 8 person's increases by 1.5 kg when a new person comes in place of one of them weighing 66 kg. What might be the weight of the new person? 1) 76 kg 2) 78 kg 3) 67.5 kg 4) Data inadequate Total weight increased = (8 × 1.5) kg = 12 kg. Weight of new person = (66 + 12) kg = 78 kg. Hence, option 2. |