7429           = 17 x 19  x 23           =17 x 19 x 23

a = - 1.25, d = - 0.25

Let the series be a₁, a₂, a₃, a₄ …

a₁ = a = - 1.25

a₂ = a₁ + d = - 1.25 - 0.25 = - 1.50

a₃ = a₂ + d = - 1.50 - 0.25 = - 1.75

a₄ = a₃ + d = - 1.75 - 0.25 = - 2.00

Clearly, the series will be 1.25, - 1.50, - 1.75, - 2.00 ……..

First four terms of this A.P. will be - 1.25, - 1.50, - 1.75 and - 2.00.

Sustainable development means that a development should meet the needs of the present without compromising the ability of future generations to meet their needs – 

(i) It is felt that the economic growth and industrialization have led to reckless exploitation of natural resources. Sustainability promotes a rational use of natural resources. 

(ii) Groundwater is an example of renewable resource. But if we use more than what is replenished by nature, then we would be overusing this resource. 

(iii) Once the non-renewable resources would be exhausted we won’t be able to use them in future. So, using the resources judiciously will help in maintaining the sustainability of development of our ecosystem.

Drawbacks of Mendeleev’s periodic table:
1. Position of hydrogen: Hydrogen is placed in group I. However, it resembles the elements of group I (alkali metals) as well as the elements of group VILA, (halogens). Therefore, the position of hydrogen in the periodic table is not correctly defined.
2. Anomalous pairs: In certain pairs of elements, the increasing order of atomic masses was not obeyed. In these cases, Mendeleev placed elements according to similarities in their properties and not in increasing order of their atomic masses. For example, argon (Ar, atomic mass 39.9) is placed before potassium (K, atomic mass 39.1). Similarly, cobalt (Co, atomic mass 58.9) is placed before nickel (Ni, atomic mass 58.6) and tellurium (Te, atomic mass 127.6) is placed before iodine (I, atomic mass 126.9). These positions were not justified.
3. Position of isotopes: Isotopes are the atoms of the same element having different atomic masses but same atomic number. Therefore, according to Mendeleev’s classification, these should be placed at different places depending upon their atomic masses. For example, isotopes of hydrogen with atomic masses 1,2 and 3 should be placed at three places. However, isotopes have not been given separate places in the periodic table.
4. Some similar elements are separated and dissimilar elements are grouped together: In the Mendeleev’s periodic table, some similar elements were placed in different groups while some dissimilar elements
had been grouped together. For example, copper and mercury resembled
in their properties but they had been placed in different groups. At the same time, elements of group IA such as Li, Na and K were grouped with copper (Cu), silver (Ag) and gold (Au), though their properties are quite different.
5. Cause of periodicity: Mendeleev did not explain the cause of periodicity among the elements.
6. Position of lanthanoids (or lanthanides) and actinoids (or actinides):
The fourteen elements following lanthanum (known as lanthanoids, from atomic number 58-71) and the fourteen elements following actinium (known as actinoids, from atomic number 90 – 103) have not been given separate places in Mendeleev’s table.
In order to cover more elements, Mendeleev modified his periodic table.

1. He generalized the study of the elements then known as the study of a mere groups.

2. In Mendeleev’s periodic table, he left some blank spaces. These vacant spaces were left for including elements that were not discovered at that time.

3. Mendeleev could also predict the properties of these unknown elements, on the basis of the properties of the elements lying adjacent to these vacant spaces.

He predicted the presence of three elements. They were named as Eka boron, Eka-aluminium and Eka-silicon. The properties of these three elements were similar to the actual elements discovered later.

Eka-boron was similar to Scandium, Eka-aluminium was similar to Gallium and Eka-silicon was similar to Germanium.

4. When noble gases were discovered later, they could be accommodated in the periodic table in the form of a separate group without disturbing the positions of the other elements.

5. He was able to correct the values of the atomic masses of elements like gold and platinum, he placed these elements going strictly by the similarities in their properties.

Anil was a writer who employed a servant Hari Singh.

Anil did not have much income but one day he came home with some money which he hid under the mattress.

The servant became greedy and stole this money but then he repented when he remembered what Anil had told him about education making him a man instead of a common thief.

This made Hari Singh return the money under the mattress.

Q u e s t i o n : भारत के सामने जो मुख्य समस्या है वह बढ़ती जनसंख्या है। (सरल वाक्य में बदलिए)

A n s w e r :

 भारत के सामने मुख्य समस्या बढ़ती जनसंख्या है।

There was a joint family of six members, including grandparents. It was the 75th birthday of my grandmother and the family planned to celebrate. her birthday. Love and Lovy, the grandson and the grand daughter were excited to celebrate their grandmother's birthday. Harish and Harsha, the parents of Love and Lovy, wanted to have dinner in a restaurant but the grandparents were reluctant to spend so much money. But when Harish and Harsha insisted, they agreed. All the six members went to a famous restaurant in the city. They decorated the table and brought some garlands for their grandparents. They all garlanded the grandparents and touched their feet. The grandparents wanted all the members to have dinner together but Harish and Harsha wanted to feed the grandparents first with their own hands. Two dishes of food were ordered and Harish started feeding his father, so did Love and Harsha, more food, started feeding grandmother followed by Lavy. When the grandparents had taken food, they ordered more food and had their dinner. When they started to leave the restaurant, a man sitting in the corner called him and told him that he had left a lot of things there. In enquiring about those things, the man said that he had set an example for the coming generations to respect their elders. Harish and Harsha were overwhelmed by his appreciation.

• Fossils are preserved remains of living organisms from remote past.
• Fossil mainly preserves only a portion of the dead organism (eg: skeleton, bone, teeth etc..)
• Fossils may vary from microscopic (single bacterial cell) to dinosaurs.

Giuseppe Mazzini He was an Italian revolutionary, who was born in Genoa in 1807. He was sent into exile at the age of 24 in 1831 for attempting a revolution in Liguria. He founded two secret societies, namely Young Italy and Young Europe. He inspired the young members of these societies to involve in revolutionary activities.
Following his ideas and on the model of his secret societies, more such societies were set up in Germany, France, Switzerland and Poland. Austrian Chancellor Duke Matternich once described him as ‘the most dangerous enemy of our social order’.

Here he refers to the tiger and he is locked in a concrete cell inside a zoo. His strength and power is bounded between four walls. He is locked and his freedom is taken from him . He could not do anything .There fore it is said His strength behind bars.

POWER is shared among different organs of government such as the legislature, judiciary and executive. It is called horizontal distribution of power because it allows different organs of government placed at the same level to exercise different powers. Such a separation ensures that none of the organs can exercise unlimited power. Each organ checks the others. This results in a balance of power amoqg various institutions. Although, judges are appointed by the executive, they can check the functioning of executive or laws made by the Legislatures. This arrangement is called a system of checks and balances.

A chemical equation has its own limitations. They do not provide information about: 

1. The physical state of reactants and products Hence, the symbols ‘s’ for solid, ‘l’ for liquid, ‘g’ for gas and ‘vap’ for vapour are added. 
2. Conditions such as temperature, pressure and catalyst affecting the reaction 
3. Concentration of reactants and products Hence, in some cases, for dilute ‘dil.’ and for concentrated ‘conc.’ are added. 
4. The nature of the chemical reaction; whether it is reversible or irreversible reaction. 
5. Speed of the reaction 
6. Heat changes accompanying the reaction; whether heat is given out or absorbed 
7. Time taken for completion of the reaction A reaction may or may not be complete, and the equation does not reveal it.

हरिहर काका वैसे तो अनपढ़ थे परन्तु उन्हें दुनियादारी की अच्छी समझ थी और इसी कारण वे अपनी जमीन किसी के नाम नहीं करते। उन्हें यह बात भलीभांति समझ आती थी सभी उनकी जायदाद के लिए उनसे संबंध बनाए हुए है।

उम्र में बहुत अधिक फासला होने पर भी लेखक और उनकी मित्रता गहरी मित्रता थी। हरिहर काका अंतर्मुखी भी थे। अपने साथ हुई दुर्घटनाओं ने उन्हें अंदर तक तोड़ दिया था इसलिए वे चुप रहते थे।

हरिहर काका साहसी भी थे महंतों और अपने भाईओं के धमकाने पर भी वे अपनी जमीन किसी के नाम नहीं करते। इस प्रकार से हरिकर काका अनपढ़ परन्तु अनुभवी, अंतर्मुखी और साहसी व्यक्ति थे।