CBSE Class 8 Mathematics Direct and Inverse Proportions Assignment Set B

Question. If x : y = 2 : 3 and 2 : x = 1 : 2, then the value of y is ____.
(A) 1/3
(B) 3/2
(C) 6
(D) 1/2
Answer : C

Question. Which of the following statements is CORRECT?
(A) Length of a side of square and its area vary directly with each other.
(B) If one angle of a triangle is kept fixed then the measure of the remaining two angles vary inversely with each other.
(C) The area of circle and its diameter vary directly with each other.
(D) All of these
Answer : D

Question. If A : B = 2 : 3 and B : C = 4 : 5, then C : A is equal to ____.
(A) 15 : 8
(B) 12 : 10
(C) 8 : 5
(D) 8 : 15
Answer : A

Question. If x varies directly as y² and x = 4 when y = 5, then find x when y is 15.
(A) 4
(B) 9
(C) 12
(D) 36
Answer : D

Question. If 1/5 : 1/x = 1/x : 1/125 then the value of x is ____.
(A) 1.25
(B) 1.5
(C) 25
(D) 2.25
Answer : C

Question. x and y vary in inverse proportion. When x is 12, y is 3. Which of the following is not a possible pair of corresponding values of x and y ?
(A) 4 and 9
(B) 10 and 3.6
(C) 72 and 0.5
(D) 5 and 6
Answer : D

Question. A labourer is paid ₹ 806 for 13 days of work. If he receives ₹ 1,798, then for how many days did he work?
(A) 29
(B) 35
(C) 60
(D) 40
Answer : A

Question. Match the following.

      P      Q     R     S
(A) 4      3      1      2
(B) 2      1      4      3
(C) 3      2      1      4
(D) 1      3      2      4
Answer : A

Question. A worker is paid ₹ 139.20 for 3 days.
(i) What will he get in the month of June (in ₹)?
(ii) For how many days will he be working for ₹ 696?
        (i)               (ii)
(A) 1392            15
(B) 15                1392
(C) 1382            20
(D) 1392            20
Answer : A

Question. 8 men can do a piece of work in 10 days.
How long will 10 men take to do the same work?
(A) 12 days
(B) 8 days
(C) 7 days
(D) 6 days
Answer : B

Question. A photograph of a bacteria enlarged 50,000 times, attains a length of 5 cm. What is the actual length of the bacteria?
(A) 2 × 10^–4 cm
(B) 10³ cm
(C) 10^–4 cm
(D) 10⁴ cm
Answer : C

Question. Match the following.

(A) P → (iv); Q → (i); R → (iii); S → (ii)
(B) P → (ii); Q → (iv); R → (iii); S → (i)
(C) P → (iv); Q → (i); R → (ii); S → (iii)
(D) P → (ii); Q → (iv); R → (i); S → (iii)
Answer : D

Question. When x = 2, 7, 11, ...., y = 8, 28, 44, ...., then x and y are in ............ .
(A) Direct proportion
(B) Inverse proportion
(C) Neither direct nor inverse proportion
(D) None of these
Answer : A

Question. In a camp there is sufficient food for 105 soldiers for 21 days. If 42 soldiers leave the camp, then how long would the food last?
(A) 30 days
(B) 35 days
(C) 65 days
(D) 45 days
Answer : B

Question. A shopkeeper has just enough money to buy 52 cycles worth ₹ 525 each. If each cycle were to cost ₹ 21 more, then number of cycles, he will be able to buy with that amount of money, is ____.
(A) 40
(B) 30
(C) 50
(D) 20
Answer : C

Question. If x and y vary inversely as each other, and x = 10 when y = 6. Find y when x = 15.
(A) 3
(B) 4
(C) 2
(D) 6
Answer : B

Question. Two quantities x and y vary inversely with each other, then ______ .
(A) x/y remains constant
(B) x – y remains constant
(C) x + y remains constant
(D) x × y remains constant
Answer : D

Question. Raghu has enough money to buy 75 machines worth ₹ 200 each. How many machines can he buy if he gets a discount of ₹ 50 on each machine?
(A) 180
(B) 200
(C) 150
(D) 100
Answer : D

Question. An agent receives a commission of ₹ 73.00 on sales of ₹ 1000.00. The commission he will get on sales of ₹ 100.00 is ____.
(A) ₹ 7.30
(B) ₹ 7.00
(C) ₹ 6.00
(D) ₹ 6.30
Answer : A

Question. In a birthday party, on an average, 5 bottles of coke are served for a group of 6 children. How many friends were present at Mohit’s party if 15 bottles of coke were used?
(A) 18
(B) 24
(C) 30
(D) 12
Answer : A

Question. Which of the following tables shows the inverse proportion?

(A) Only (i)
(B) Both (i) and (ii)
(C) Both (ii) and (iii)
(D) None of these
Answer : A

vA cistern has two inlets A and B which can fill it in 12 minutes and 15 minutes respectively. An outlet C can empty the full cistern in 10 minutes. If all the three pipes then are opened together in the empty cistern, time taken to fill the cistern
completely is ____.
(A) 20 minutes
(B) 10 minutes
(C) 15 minutes
(D) 5 minutes
Answer : A

Question. In 15 days, the earth picks up 1.2 × 108 kg of dust from the atmosphere. In how many days it will pick up 4.8 × 108 kg of dust?
(A) 50
(B) 40
(C) 60
(D) 100
Answer : C

Question. State ‘T’ for true and ‘F’ for false.
(i) If x and y are in direct proportion, then
(x – 1) and (y – 1) are also in direct proportion.
(ii) If x and y are in inverse proportion then (x + 2) and (y + 2) are also in inverse proportion.
(iii) Two quantities x and y are said to vary directly with each other if x/y = k, where k is a positive constant.
(iv) When distance is kept fixed, then speed and time vary inversely with each other.
     (i)      (ii)     (iii)     (iv)
(A) T        F        F        T
(B) T        T        F        F
(C) F        F        T        T
(D) T        F        T        F
Answer : C

Question. Fill in the blanks.
(i) The perimeter of circle and its diameter vary P with each other.
(ii) If two quantities p and q vary inversely with each other then Q of their corresponding values remain constant.
(iii) When x and y are in indirect proportion and if y doubles then x becomes  R 
           P                     Q               R
(A) Inversely         Ratio           Double
(B) Directly           Product       Half
(C) Inversely        Ratio            Half
(D) Directly           Product       Double
Answer : C

Click on link below to download CBSE Class 8 Mathematics Direct and Inverse Proportions Assignment Set B