In a class test, the sum of Shefali's marks in Mathematics and English is 30.
[question] Question. In a class test, the sum of Shefali's marks in Mathematics and English is 30. Had she got 2 marks more in Mathematics and 3 marks less in English, the product of their marks would have been 210. Find her marks in the two subjects. [/question] [solution] Solution: Let the marks in Maths be x. Then, the marks in English will be 30 – x. According to the given question, (x+2)(30-x-3)=210 $(x+2)(27-x)=210$ $\Rightarrow-x^{2}+25 x+54=210$ $\Rightarrow x^{2}-25 x+156=0$ $\Rightarro...
Read More →Calculate the mass percent of different elements
[question] Question. Calculate the mass percent of different elements present in sodium sulphate $\left(\mathrm{Na}_{2} \mathrm{SO}_{4}\right)$. [/question] [solution] Solution: The molecular formula of sodium sulphate is $\mathrm{Na}_{2} \mathrm{SO}_{4}$. Molar mass of $\mathrm{Na}_{2} \mathrm{SO}_{4}=[(2 \times 23.0)+(32.066)+4(16.00)]$ $=142.066 \mathrm{~g}$ Mass percent of an element $=\frac{\text { Mass of that element in the compound }}{\text { Molar mass of the compound }} \times 100$ Mas...
Read More →In which of the following examples of motion,
[question] Question. In which of the following examples of motion, can the body be considered approximately a point object: (a) a railway carriage moving without jerks between two stations. (b) a monkey sitting on top of a man cycling smoothly on a circular track. (c) a spinning cricket ball that turns sharply on hitting the ground. (d) a tumbling beaker that has slipped off the edge of a table. [/question] [solution] solution: Answer: (a), (b) (a) The size of a carriage is very small as compare...
Read More →Why are manures and fertilisers used in fields ?
[question] Question. Why are manures and fertilisers used in fields ? [/question] [solution] Solution: The manures and fertilisers are the main sources of nutrient supply to crops. They are used to ensure good vegetative growth (leaves, branches and flowers), giving rise to healthy plants, which results in high crop production. [/solution]...
Read More →Explain any one method of crop production which ensures high yield.
[question] Question. Explain any one method of crop production which ensures high yield. [/question] [solution] Solution: Inter cropping is a method of crop production which ensures high yield. Inter cropping is a practice of growing two or more crops simultaneously in the same field in rows. (i) In inter cropping definite row patterns like 1 : 1, 1 : 2, or 1 : 3 are followed 1 : 1 row pattern means that there is one row of main crop with one row of intercrop. (ii) In inter cropping, there is a ...
Read More →The sum of the reciprocals of Rehman's ages (in years) 3 years ago and 5 years from now is 1/3.
[question] Question. The sum of the reciprocals of Rehman's ages (in years) 3 years ago and 5 years from now is 1/3. Find his present age. [/question] [solution] Solution: Let the present age of Rehman be x years. We are given that $\frac{\mathbf{1}}{\mathbf{x}-\mathbf{3}}+\frac{\mathbf{1}}{\mathbf{x}+\mathbf{5}}=\frac{\mathbf{1}}{\mathbf{3}}$ $\Rightarrow \frac{x+5+x-3}{(x-3)(x+5)}=\frac{1}{3}$ $\Rightarrow 3(2 x+2)=(x-3)(x+5)$ $\Rightarrow 6 x+6=x^{2}+2 x-15$ $\Rightarrow x^{2}-4 x-21=0$ $a=1,...
Read More →What is pasturage and how is it related to honey production ?
[question] Question. What is pasturage and how is it related to honey production ? [/question] [solution] Solution: Pasturage is flora or crop available to honey bee for collection of nectar and pollen. Pollen is food for honey bees. Nectar is transformed into honey. The amount and quality of honey depend upon type and extent of pasturage. [/solution]...
Read More →Calculate the molecular mass of the following
[question] Question. Calculate the molecular mass of the following (i) $\mathrm{H}_{2} \mathrm{O}$ (ii) $\mathrm{CO}_{2}$ (iii) $\mathrm{CH}_{4}$ [/question] [solution] Solution: (i) $\mathrm{H}_{2} \mathrm{O}:$ The molecular mass of water, $\mathrm{H}_{2} \mathrm{O}$ = (2 × Atomic mass of hydrogen) + (1 × Atomic mass of oxygen) = [2(1.0084) + 1(16.00 u)] = 2.016 u + 16.00 u = 18.016 = 18.02 u (ii) $\mathrm{CO}_{2}$ : The molecular mass of carbon dioxide, $\mathrm{CO}_{2}$ = (1 × Atomic mass of ...
Read More →Find the roots of the following equations :
[question] Question. Find the roots of the following equations : (i) $x-\frac{\mathbf{1}}{\mathbf{x}}=3, x \neq 0$ (ii) $\frac{1}{x+4}-\frac{1}{x-7}=\frac{11}{30}, x \neq-4,7$ [/question] [solution] Solution: (i) $x-\frac{1}{x}=3 \quad \Rightarrow x^{2}-3 x-1=0$ On comparing this equation with $a x^{2}+b x+c=0$ we obtain $\mathrm{a}=1, \mathrm{~b}=-3, \mathrm{c}=-1$ By using quadratic formula, we obtain $x=\frac{-b \pm \sqrt{b^{2}-4 a c}}{2 a} \Rightarrow x=\frac{3 \pm \sqrt{9+4}}{2}$ $\Rightarr...
Read More →What are the desirable characters of bee varieties suitable for honey production?
[question] Question. What are the desirable characters of bee varieties suitable for honey production? [/question] [solution] Solution: (i) Gentleness in nature (ii) Good honey collection (iii) Prolific queen (iv) Less swarming (v) Ability to protect itself from enemies. [/solution]...
Read More →What are the advantages of composite fish culture ?
[question] Question. What are the advantages of composite fish culture ? [/question] [solution] Solution: (i) There is no competition for food or space amongst different types of fish. (ii) Food available in different part of the pond are utilized due to their different food habits and different habitats. (iii) The fish yield is high as some six types of fish are growing simultaneously. [/solution]...
Read More →How are fishes obtained ?
[question] Question. How are fishes obtained ? [/question] [solution] Solution: There are two methods of obtaining fish, capture fishery (capturing fish) from natural waters and culture fishery in impounded waters. In both cases the fish are caught with the help of nets. [/solution]...
Read More →Find the roots of the quadratic equations given in
[question] Question. Find the roots of the quadratic equations given in Q.1 above by applying the quadratic formula. [/question] [solution] Solution: (i) $2 x^{2}-7 x+3=0$ $a=2, b=-7, c=3$ Discriminant $D=(-7)^{2}-4(2)(3)=25$ $\Rightarrow \sqrt{10}=\sqrt{25}=5$ Roots of the given quadratic equation are $\frac{-\mathbf{b} \pm \sqrt{\mathbf{D}}}{\mathbf{2 a}}$ i.e., $\frac{\mathbf{7} \pm \mathbf{5}}{\mathbf{2} \times \mathbf{2}}$, i.e., the roots are 3 and $\frac{\mathbf{1}}{\mathbf{2}}$. (ii) $2 ...
Read More →What are the differences between broilers and layers and in their management ?
[question] Question. What are the differences between broilers and layers and in their management ? [/question] [solution] Solution: Broilers are fast growing young chicken of 6–10 weeks age which are known for the good quality and taste of their meat. Layers are sexually mature hens which are raised for egg laying. Broilers are given diet rich in protein, with adequate fat, vitamins A and K. They are provided with best of space, hygiene and temperature. Layers are given inferior quality feed. L...
Read More →What management practices are common in dairy and poultry farming ?
[question] Question. What management practices are common in dairy and poultry farming ? [/question] [solution] Solution: (i) Proper shelter, its hygiene, aeration and lighting. (ii) Proper feed and feed additives. Drinking water. (iii) Health care including vaccination. [/solution]...
Read More →Find the roots of the following quadratic equations,
[question] Question. Find the roots of the following quadratic equations, if they exist, by the method of completing the square (1) $2 x^{2}-7 x+3=0$ (ii) $2 x^{2}+x-4=0$ (iii) $4 x^{2}+4 \sqrt{3} x+3=0$ (iv) $2 x^{2}+x+4=0$ [/question] [solution] Solution: (i) $2 x^{2}-7 x+3=0$ $\Rightarrow 4 x^{2}-14 x+6=0$ $\Rightarrow(2 x)^{2}-7(2 x)+6=0$ $\Rightarrow y^{2}-7 y+6=0$ where $y=2 x$ $\Rightarrow\left\{\mathbf{y}^{2}-\frac{7}{2} \mathbf{y}-\frac{7}{2} \mathbf{y}+\left(-\frac{7}{2}\right)^{2}\rig...
Read More →Discuss the implications of the following statement
[question] Question. Discuss the implications of the following statement "It is interesting to note that poultry is India's most efficient converter of low fibre food stuff (which is unfit for human consumption) into highly nutritious animal protein food. [/question] [solution] Solution: India is basically agriculture society where a lot of wastes are produced during food processing, e.g., fish meal, meat meal, rice bran, etc. They are profitably used in forming poultry feed. In return poultry p...
Read More →Which method is commonly used for improving the cattle breeds and why?
[question] Question. Which method is commonly used for improving the cattle breeds and why? [/question] [solution] Solution: Cross breeding indigenous breeds with exotic breeds. Foreign or exotic breeds have higher milk yield and longer lactation period as compared to indigenous breeds. Therefore, indigenous breeds should be cross-breeded with exotic breeds. The local breeds are hardy and resistant to several diseases. [/solution]...
Read More →Say True or False.
[question] Question. Say True or False. (i) COPRA applies only to goods. (ii) India is one of the many countries in the world which has exclusive courts for consumer redressal. (iii) When a consumer feels that he has been exploited, he must file a case in the District Consumer Court. (iv) It is worthwhile to move to consumer courts only if the damages incurred are of high value. (v) Hallmark is the certification maintained for standardisation of jewellry. (vi) The consumer redressal process is v...
Read More →What factors may be responsible for losses of grains during storage?
[question] Question. What factors may be responsible for losses of grains during storage? [/question] [solution] Solution: During the storage of grains, various biotic factors such as insects, rodents, mites, fungi, bacteria, etc. and various abiotic factors such as inappropriate moisture, temperature, lack of sunlight, flood, etc. are responsible for losses of grains. These factors act on stored grains and result in degradation, poor germinability, discoloration, etc. [/solution]...
Read More →Match the following.
[question] Question. Match the following. [/question] [solution] Solution: [/solution]...
Read More →It is claimed that two cesium clocks,
[question] Question. It is claimed that two cesium clocks, if allowed to run for 100 years, free from any disturbance, may differ by only about $0.02 \mathrm{~s}$. What does this imply for the accuracy of the standard cesium clock in measuring a time-interval of 1 s? [/question] [solution] solution: Difference in time of caesium clocks = 0.02 s Time required for this difference = 100 years $=100 \times 365 \times 24 \times 60 \times 60=3.15 \times 10^{9} \mathrm{~s}$ In $3.15 \times 10^{9} \math...
Read More →Why should preventive measures and biological
[question] Question. Why should preventive measures and biological control methods be preferrdfor protecting crops? [/question] [solution] Solution: Preventive measures and biological control methods should be preferred for protecting crops because excessive use of chemicals leads to environmental problems. These chemicals are also poisonous for plants and animals. Preventive measures include proper soil and seed preparation, timely sowing of seeds, intercropping and mixed cropping, usage of res...
Read More →The altitude of a right triangle is 7 cm less than its base.
[question] Question. The altitude of a right triangle is 7 cm less than its base. If the hypotenuse is 13 cm, find the other two sides. [/question] [solution] Solution: In $\triangle \mathrm{ABC}$, base $\mathrm{BC}=\mathrm{x} \mathrm{cm}$ and altitude $A C=(x-7) \mathrm{cm}$ $\angle \mathrm{ACB}=90^{\circ}$ $\mathrm{AB}=13 \mathrm{~cm}$ By Pythagoras theorem, we have $\mathrm{BC}^{2}+\mathrm{AC}^{2}=\mathrm{AB}^{2}$ $\Rightarrow x^{2}+(x-7)^{2}=13^{2}$ $\Rightarrow x^{2}+x^{2}-14 x+49=169$ $\Ri...
Read More →Critically examine the progress of consumer movement in India.
[question] Question. Critically examine the progress of consumer movement in India. [/question] [solution] Solution: The consumer movement in India has evolved vastly since it began. There has been a significant change in consumer awareness in the country. Till the enactment of COPRA in 1986, the consumer movement did not bear much force, but ever since its inception, the movement has been empowered substantially. The setting up of consumer courts and consumer groups has been a progressive move....
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