Class 8 ample book chapter 2 objective solutions
Answers
Answer:
1.Which of the following is not a linear equation in one variable?
A. 33
B. 33(x+y)
C. 33x
D. 33y
Answer: B
Explanation: In 33(x+y), x and y are two variables.
2. The solution of 2x-3=7 is:
A. 5
B. 7
C. 12
D. 11
Answer: A
Explanation: 2x-3=7
2x=7+3=10
x=10/2 = 5
Explanation:
The solution of 2y + 9 = 4 is:
A. 9/2
B. 4/9
C. -⅖
D. -5/2
Answer: D
Explanation: 2y+9 = 4
2y = 4-9 = -5
y=-5/2
4. The solution of y/5 = 10 is:
A. 15
B. 10
C. 50
D. 5
Answer: C
Explanation: y/5 = 10
y = 5×10 = 50
5. What should be added to -7/3 to get 3/7?
A. 21/58
B. 58/21
C. 47/21
D. 50/21
Answer: B
Explanation: Let the number be x
-7/3+x = 3/7
x=3/7+7/3 = (9+49)/21 = 58/21
6. The perimeter of rectangle is 20cm. If the length of rectangle is 6cm, then its breadth will be:
A. 4 cm
B. 6 cm
C. 10 cm
D. 14 cm
Answer: A
Explanation: Perimeter of rectangle = 2(Length+Breadth)
20 = 2(6+x)
6+x = 20/2
6+x = 10
x = 10-6
x=4 cm
7. The age of father is three times the age of son. If the age of son is 15 years old, then the age of father is:
A. 50 years
B. 55 years
C. 40 years
D. 45 years
Answer: D
Explanation: Let age of the father is x
Given: x = 3 × (age of son) = 3 × (15) = 45 years
8. The difference between two whole numbers is 66. The ratio of the two numbers is 2 : 5. The two numbers are:
A. 60 and 6
B. 100 and 33
C. 110 and 44
D. 99 and 33
Answer: C
Explanation: Let the two numbers be 2x and 5x since they are in the ratio of 2:5.
The difference between 5x and 2x = 66
5x – 2x = 66
3x = 66
x = 22
Hence, 2x = 2(22) = 44 and 5x = 5(22) = 110.
9. Three consecutive integers add up to 51. The integers are:
A. 16,17,18
B. 15,16,17
C. 17,18,19
D. 18,19,20
Answer: A
Explanation: Let the three consecutive integers be x, x+1, x+2
x+(x+1)+(x+2) = 51
3x+3 = 51
3x = 51 – 3
x = 48/3 = 16
x+1 = 16+1=17
x+2 = x+2 = 18
10. The solution for 3m = 5m – (8/5) is:
A. 8/5
B. ⅘
C. 5/4
D. 4/3
Answer: B
Explanation: 3m = 5m – (8/5)
8/5 = 5m – 3m
2m = 8/5
m = 8/10 = 4/5
Explanation:
Which of the following is a disease caused by protozoans?
Answer: (C) Malaria
Solution:
∙ Protozoans are eukaryotic, unicellular microorganisms. Most of them are free-living, found in soil and fresh water, while some are parasitic and cause diseases in plants and animals. Malaria is caused by the protozoan parasite, Plasmodium.
∙ Tuberculosis (TB) is caused by a type of bacterium called Mycobacterium tuberculosis.
∙ Polio is a highly contagious infectious disease caused by polio virus.
∙ Typhoid fever is an acute infectious illness associated with fever that is most often caused by the Salmonella typhi bacteria.
2. Which of the following diseases is caused by a bacteria
Answer: (B) Tuberculosis
Solution:
∙ Tuberculosis is an air-borne disease caused by the bacterial species Mycobacterium tuberculosis.
∙ Polio, dengue and chicken pox are viral diseases caused by Picornavirus, Flavivirus and chicken pox virus respectively.
3. Some plants have nitrogen-fixing bacteria in their root nodules. What are these bacteria called?
Answer: (D) Rhizobium
4. In order to take precautionary steps to control dengue, we must take measures to stop the breeding of:
Answer: (A) Aedes mosquito
5. Partial sterilization of a product such as milk at a high temperature is known as?
Answer: (A) Pasteurizatio
6. Living organisms which are invisible to the naked eye are called _________ .
Answer: (C) Microorganisms
7. Which of the following is a communicable disease?
Answer: (B) Chicken pox
8. Vacs are made up of a
Answer: (B) Weak microorganisms
9. The bacterium present in curd is:
Answer: (B) Lactobacillus
10. While baking cakes, yeast reproduces rapidly and produces ___ gas.
Answer: (C) carbon dioxide
11. ______ is used for the production of alcohol and wine.
Answer: (A) yeast
12. Which of the following diseases can be cured using antibiotics?
Answer: (C) Typhoid
13. Which organisms are microscopic and dependent on host organisms for reproduction?
AnsweWhich of the following is a disease caused by protozoans?
Answer: (C) Malaria
2. Which of the following diseases is caused by a bacteria?
Answer: (B) Tuberculosis
3. Some plants have nitrogen-fixing bacteria in their root nodules. What are these bacteria called?
Answer: (D) Rhizobium
4. In order to take precautionary steps to control dengue, we must take measures to stop the breeding of:
Answer: (A) Aedes mosquito
5. Partial sterilization of a product such as milk at a high temperature is known as
Answer: (A) Pasteur
6. Living organisms which are invisible to the naked eye are called _________ .
Answer: (C) Microorganisms
7. Which of the following is a communicable disease?
Answer: (B) Chicken pox
8. Vaccines are made up
Answer: (B) Weak microorganisms
9. The bacterium present in curd is:
Answer: (B) Lactobacillus
10. While baking cakes, yeast reproduces rapidly and produces ___ gas.
Answer: (C) carbon dioxide
11. ______ is used for the production of alcohol and wine
Answer: (A) Yeast
12. Which of the following diseases can be cured using antibiotics?
Answer: (C) Typhoid
13. Which organisms are microscopic and dependent on host organisms for reproduction?
Answer: (C) Virus
14. _______ are the agents that act as carriers of a pathogen and spread disease
Answer: (A) Vectors
15. An infectious disease is ___________
Answer: (B) spread from person to person
16. Which one of the following is not a method of food preservat
Answer: (C) Boiling
17. Which among the following statements is not associated with food preservation?
Answer: (B) Decreased shelf life
18. Which one of the following is not produced by the process of fermentation?
Answer: (B) Milk
19. A plant disease called citrus canker is caused by a _________ .
Answer: (A) Bacteria
20. Which among the following pathogens causes cholera?
Answer: (A) Bacteria
r: (C) Viruses
Solution: Viruses are non-cellular microorganisms composed of protein, nucleic acids and lipids. Viruses are considered both living and non-living organisms. They are active inside host cells and reproduce inside them by infecting living cells. Outside a host it is considered non-living as it does not have a cellular machinery of its own.
14. _______ are the agents that act as carriers of a pathogen and spread diseases.
Answer: (A) Vectors
15. An infectious disease is ___________ .
Answer: (B) spread from person to person
16. Which one of the following is not a method of food preserval
Answer: (C) Boiling
17. Which among the following statements is not associated with food preservation?
Answer: (B) Decreased shelf life
18. Which one of the following is not produced by the process of fermentation?
Answer: (B) Milk
Solution: The breakdown of carbon containing substances like carbohydrates in the absence of oxygen by microorganisms like yeast and bacteria is termed as fermentation. Fermentation is involved in making bread, vinegar, yoghurt, wine, cider, cocoa, cheese etc.
19. A plant disease called citrus canker is caused by a _________ .
Answer: (A) Bacteria
20. Which among the following pathogens causes cholera?
Answer: (A) Bacteria