Averages
Practice Questions on Averages
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Q14) Average of a, b and c is 11; average of c, d and e is 17; average of e and f is 22; and average of c and e is 16. Find out the
average of a, b, c, d, e and f. 1) 15.66 2) 18.5 3) 21.33 4) 16.5 a + b + c = 11*3 = 33; .... 1 c + d + e = 17*3 = 51; .... 2 e + f = 22*2 = 44; .... 3 e + c = 17*2 = 34; .... 4 From equation 2 and 4, we get 34 + d = 51 or d = 17 .... 5 Adding equation 1, 3 and 5 we get a + b + c + d + e + f = 33 + 17 + 44 = 94 Required average = 94/6 = 15.66 Hence, option 1. Q15) Pinky bought 20 books each for Rs 10, 45 pens each for Rs 5 and 15 pencils each for Rs 3. Calculate the average price of all the stationary goods? 1) Rs 6 2) Rs 4.8 3) Rs 5.875 4) None of these Required average = (20*10 + 45*5 + 15*3)/(20 + 45 + 15) = Rs 5.875 Hence, option 3. Q16) In a family there are 8 members. Average age of the grandparents is 77 years, Average age of the parents is 50 years. Average age of the two youngest children is 20 years, whereas the average age of the eldest child and his wife is 24 years. Find the average age of the family? 1) 42.75 years 2) 42.25 years 3) 42.375 years 4) 42.625 years As average age of grandparents is 77 years. Hence, sum of the ages of the grandparents is 154 years. As average age of parents is 50 years. Hence, sum of the ages of the parents is 100 years. Average age of the two youngest children is 20 years. Hence, sum of their ages is 40 years. Average age of the eldest child and his wife is 24 years. Hence, sum of their ages is 48 years. Average age of the family = (154 + 100 + 40 + 48 )/8 = 42.75 Hence, option 1. Q17) Consider the set S = {2, 3, 4, 5,……, 2n + 1}, where n is a positive integer larger than 1520. 'X' is defined as the average of odd integers in S and 'Y' is defined as the average of even integers in S. What is the value of X-Y ? 1) 760 2) 1 3) (n + 1)/2n 4) 1520 Value of X - Y would be same for n > 1520 and n ≤ 1520. Hence, we can substitute a smaller value of ‘n’. Say n = 2 If n = 2 the S = {2, 3, 4, 5} (2n + 1 is equal to 5 when n = 2) In this case X = 4 (average of odd integers in S) Y = 3 (average of even integers in S) Hence, X - Y = 4 - 3 = 1 Hence, option 2. Q18) Three classes: P, Q, and R, take an algebra test. The average score of class P is 81. The average score of class Q is 76. The average score of class R is 85. The average score of all students in classes P and Q together is 79. The average score of all students in classes Q and R together is 81. What is the average for all the three classes? 1) 79.5 2) 81.5 3) 81 4) Data Inadequate Average score of class P is 81 and that of class Q is 76 and the combined average score of P and Q is 79. So, ratio of students in the two classes i.e. P:Q = 3:2. Similarly, average score of class Q is 76 and that of class R is 85 and the combined average score of Q and R is 81. So, ratio of students in the two classes i.e. Q:R = 4:5. Therefore, P : Q : R = 6 : 4 : 5 Total average for P, Q and R  Hence, option 3. |