EXERCISE 6.A (OBJECTIVE TYPE QUESTIONS) (IN 51 55 SOLUTION)

51.   A pupil’s marks were wrongly entered as 83 instead of 63. Due to that the average marks for the class got increased by half. The number of pupils in the class is:

a)      10

b)      20

c)       40

d)      73

52.   The average age of 15 students of a class is 15 years. Out of these, the average age of 5 students is 14 years and that of the other 9 students is 16 years. The age of the 15^th student is:

a)      11years

b)      14 years

c)       15 years

d)      15 2/7 years.

53.   The average of 11 numbers is 10.9. If the average of the first six numbers is 10.5 and that of the last six numbers is 11.4 then  the middle number is:

a)      11

b)      11.3

c)       11.4

d)      11.5

54.   The average weight of three boys A,B and C is 54 1/3 kg, while the average weight of three boys B,D and E is 53 kg. What is the average weight of A, B, C, D and E?

a)      52.4 kg

b)      53.2 kg

c)       53.8 kg

d)      Data inadequate

e)      None of these

55.   The average temperature of the town in the first four days of a month was 58 degrees. The average for the second, third, fourth and fifth days was 60 degrees. If the temperatures of the first and fifth days were in the ratio 7: 8, then what is the temperature on the fifth day?

a)      64 degrees

b)      62 degrees

c)       56 degrees

d)      None of these

     ANSWERS

      51.C

     52.A

     53.D

    54.D

    55.A

SOLUTION

 51.   Let there be X pupils in the class.

Total increase in marks = (X x ½) = x/2.

X / 2 = (83 – 63)    X / 2 = 20  X = 40.

52.   Age of the 15^th student = [15 x 15 –(14 x 5 + 16 x 9)] = (225 – 214) = 11 years.

53.   Middle number = [(10.5 x 6 + 11.4 x 6) – 10.9 x 11] = (131.4 – 119 .9) = 11.5.

54.   Total weighty of (A + B + C) = (54 1/3 x 3) kg = 163 kg.

Total weight of (B +D + E ) = (53 x 3) kg = 159 kg.

Adding both, we get: A + 2B+ C + D + E = (163 + 159) kg = 322 kg.

So, to find the average weight of A, B C, D and E, we ought to know B’s weight, which is not given. So, the data is inadequate.

55.   Sum of temperatures on 1^st, 2^nd, 3^rd and 4^th days = (58 x 4) = 232 degrees …(I).

Sum of temperatures on 2^nd, 3^rd, 4^th and 5^th days = (60 x 4) = 240 degrees…(II)

Subtracting (I) from (II), we get:

Temp. on 5^th day – temp. on 1 st day = 8degrees.

Let the temperatures o n 1^st and 5^th days be 7 x and 8 x degrees respectively.

Then, 8x – 7x = 8 or x = 8.

Temperature on the 5^th day = 8 degrees.

Let the temperatures on 1^st and 5^th days be 7x and 8x degrees respectively.

Then, 8x – 7x = 8 or x = 8.

Temperature on the 5^th day = 8x = 64 degrees.