ROTATIONAL SYMMETRY IN A PLANE

When we say that a figure has rotational symmetry we mean that it is possible to rotate it about a center in such a way that the whole figure is unchanged but the parts of it have been rotated. The number of ways in which this can be done is called the order of rotational symmetry, and it is usual to count the identity operation (rotation through 0 degree or 360 degree, and so on) as one of the symmetries. Any figure has the trivial rotational symmetry of order one about any point. The letter N, the parallelogram and many other familiar figures, have rotational symmetry of order two.

THE TRAPEZIUM

There is one more special type of quadrilateral which frequently occurs in practical work, the trapezium; this is a quadrilateral with just one pair of opposite sides parallel.

In the side figure, this is a trapezium ABCD with an axis of symmetry. Such a figure is called an isosceles trapezium.

BUSINESS CALCULATIONS

The custom of charging interest on loans must be as old as money itself. Merchants and moneylenders have always tried to make a profit and to relate the profit to the size of transaction; a big deal calls for a big profit.

Roman taxes were usually 1/20, 1/25, or 1/100 of the quantity involved, and these fractions may have led to the practice of working in hundredths, or percentages. During the middle ages calculation of profit or interest as so much in a hundred became the common practice and the phrase per cent was established. This phrase was abbreviated in many different ways; one of the abbreviations was P0c and it is thought that the modern symbol % may have been derived from this.

One of the earliest examples of the phrase ‘per cent’occurs in the Liber Abaci by Leonardo of Pisa, published in 1202, where the author uses it in a problem concerning a merchant who is to sell wool in Florence at a profit of 20 per cent

ALBERT EINSTEIN

Albert Einstein (pronounced /ˈælbərt ˈaɪnstaɪn/; German: [ˈalbɐt ˈaɪnʃtaɪn]; 14 March 1879 – 18 April 1955) was a theoretical physicist, philosopher and author who is widely regarded as one of the most influential and best known scientists and intellectuals of all time. A German-Swiss Nobel laureate, he is often regarded as the father of modern physics.^[3] He received the 1921 Nobel Prize in Physics "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect".^[4]

His many contributions to physics include the special and general theories of relativity, the founding of relativistic cosmology, the first post-Newtonian expansion, the explanation of the perihelion precession of Mercury, the prediction of the deflection of light by gravity (gravitational lensing), the first fluctuation dissipation theorem which explained the Brownian motion of molecules, the photon theory and the wave-particle duality, the quantum theory of atomic motion in solids, the zero-point energy concept, the semi-classical version of the Schrödinger equation, and the quantum theory of a monatomic gas which predicted Bose–Einstein condensation.

Einstein published more than 300 scientific and over 150 non-scientific works; he additionally wrote and commentated prolifically on various philosophical and political subjects.^[5] His great intelligence and originality has made the word "Einstein" synonymous with genius.

Referred from Wikipedia 

SCALES

The scale of a map is often given in the form 1 : 100.000, or 1 : 25.000, that is as a ratio 1 : n. The scale 1 : 25.000 means that 1 cm on the map represents 25.000 cm or 0,25 km on the ground. When 1 : n is given the scale of a map it is called the representative fraction (R.F.) on the map.