Average

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Directions: Each of the questions given below is followed by series of options among which you have to choose the best one. You can also review your choices by clicking into answer section.


1. If a, b, c, d, e are five consecutive odd numbers, their average Is:

A.5(a + 4)

B.5(a+b+c+d+e)

C.abcde

D.(a + 4)


Answer

                  Ans: Option D

       Explanation:

       Clearly, b=a+2,c=a+4,d=a+6 and e=a+8.

       Average (a + (a + 2) + (a + 4) + (a + 6) + (a + 8)) / 5

       = (5a + 20) / 5 = (a + 4)


2. The average of non-zero number and its square is 5 times the number. The number is:

A. 9

B. 17

C. 29

D. 295


Answer

                  Ans: Option A

       Explanation:

       Let the number be x. then,

       x+x2/2= 5x

       x2– 9=0

      x(x-9)=0

      x=0 or x=9

      So, the number is 9


3. The average of 20 numbers is zero. Of them, at the most, how many may be greater than zero?

A.0

B.1

C.10

D.19


Answer

                  Ans: Option A

       Explanation:

      Average of 20 numbers = 0.

      Sum of 20 numbers (0 x 20) = 0.

      It is quite possible that 19 of these numbers may be positive and if their sum is a then 20th number is (-a).


4. Find the average of all the numbers between 6 and 34 which are divisible by 5.

A. 18

B. 20

C. 24

D. 30


Answer

                  Ans: Option B

       Explanation:

       Average= (10+15+20+25+30/5)= 100/5= 20


5. The average of ten numbers is 7. If each number is multiplied by 12, then the average of new set of numbers is :

A.7

B.82

C.19

D.84


Answer

                  Ans: Option D

       Explanation:

       Average of new set = (12 x 7) = 84.


6. The average age of our family of four is 35. Excluding me, the average age is 40. Find my age.

A. 20

B. 25

C. 30

D. 15


Answer

                  Ans: Option A

       Explanation:

       Let

      My age is

      Sum of all 4 ages =35*4 = 140

      Average age excluding me =(140-x)/3 = 40

      x=20


7. Arun obtained 76, 65, 82, 67 and 85 marks (out in 100) in English, Mathematics, Chemistry, Biology and Physics. What is his average mark?

A. 53

B. 54

C. 72

D. 75


Answer

                  Ans: Option D

       Explanation:

       Average mark = (76+65+82+67+85)/5

       =375/5=75


8. A set S contains eight positive integers. If each of these numbers is increased by 5%, the average of the set increases by

A. 40%

B. 8%

C. 5%

D. 20%


Answer

                  Ans: Option C

       Explanation:       

       If the average of all numbers in a set is increased equally, the average of the set also increases equally.

       So, the average of the set increases by 5%.


9.  The average weight of A, B and C is 45 kg. If the average weight of A and B be 40 kg and that of B and C be 43 kg, then the weight of B is:

A.17 kg

B.20 kg

C.26 kg

D.31 kg


Answer

                  Ans: Option D

       Explanation:

      Let A, B, C represent their respective weights. Then, we have:

      A + B + C = (45 x 3) = 135 …. (i)

      A + B = (40 x 2) = 80 …. (ii)

      B + C = (43 x 2) = 86 ….(iii)

      Adding (ii) and (iii), we get: A + 2B + C = 166 …. (iv)

      Subtracting (i) from (iv), we get: B = 31.

      B's weight = 31 kg.


10. Find the average of the first ten multiples of 3.

A. 30

B. 15

C. 18

D. 16.5


Answer

                  Ans: Option D

       Explanation:

       Sum of the first 10 multiples of 3 = 3+6+9+…+30 = 3*(1+2+..+10)

       = 3*(10*11/2) = 165

       Average = 165/10 = 16.5


11. A team of 8 persons joins in a shooting competition. The best marksman scored 85 points. If he had scored 92 points; the average score for the team would have been 84. The number of points, the team scored, was :

A. 672

B.645

C.665

D. 588


Answer

                  Ans: Option C

       Explanation:

       Let the total score be x.

       (x +92 – 85)/8 = 84 so x+7 = 672 so x=665


12. If the average of x and y is 30 and the average of y and z is 20, find x-z.

A. 10

B. 15

C. 30

D. 20


Answer

                  Ans: Option D

       Explanation:

       Let,

       (x+y)/2 = 30

       x+y=60

       (y+z)/2 = 20 & y+z=40

       x-z = (x+y)-(y+z) = 20


13. The average age of boys in a class is 16 years and that of the girls is 15 years. What is the average age for the whole class?

A. 15

B. 16

C. 15.5

D. Insufficient Data


Answer

                  Ans: Option D

       Explanation:

       We do not have the number of boys and girls. Hence we cannot find out the answer.


14. The average mark of a class in a science test is 75. Geetha was the topper with 96 marks. If her mark was wrongly entered as 69, the average of the class decreases by 1. Find the number of students in the class.

A. 45

B. 37

C. 27

D. 25


Answer

                  Ans: Option C

       Explanation:

       Let, the number of students be x.

       Sum of all marks = 75x (75x-96+69)/x = 74 x=27


15.  A library has an average of 510 visitors on Sundays and 240 on other days. The average number of visitors per day in a month of 30 days beginning with a Sunday is:

A.250

B.276

C.280

D.285


Answer

                  Ans: Option D

       Explanation:

       Since the month begins with a Sunday, to there will be five Sundays in the month.

       Required average =   (510 x 5 + 240 x 25)/30

       = 8550/30

       = 285


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