Вопрос школьника по предмету Математика
Закройщики обуви в течение месяца сэкономили 7 236 дм кожи. Если на одну пару обуви требуется 18 дм, то сколько дополнительно пар обуви можно сшить из сэкономмленной кожи?
Ответ учителя по предмету Математика
1) 7236÷18=402 (пары) — можно сшить из сэкономленной кожи.
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The metric system
Physics measures such physical quantities as time, length, mass,
density, velocity, area, volume, temperature and energy. Different units
of length and mass exist. Nearly all of them are interrelated. Nowadays,
three main systems of measurement are widely used: the British system
of unity, the metric system of units and the International system of units
(SI).
With a few exceptions, all the nations of the world use the metric
system. It is so easy that anyone who knows arithmetic can learn it
quickly. Before the introduction of the metric system (metre-kilogramsecond), the British foot-pound-second system was widely used. But
the latter system (which is still in use in Great Britain and the USA)
was very complicated and caused serious difficulties in the international
trade. Fox example, in the British system 1 mile is equal to 1760 yards,
1 yard – to feet and 1 foot – to 12 inches. This means that it’s very difficult to convert units. But in the metric system each unit is a multiple of
the following lower unit by ten. Therefore, the conversion to a higher 11
quantity is done by moving the decimal point to the right to the required
number of places, and vice versa.
The idea of decimal system was realized only at the end of the 18th
century. In 1791, the French Academy of Science decided that the standard of length should be one ten-millionth part of the distance from the
Equator to the North Pole. The two French scientists charged with the
task took this distance on a line running through Paris and divided it into 10000000 equal parts. They called one of the parts a metre(‗measure‘), which became the main unit. Metre was also used to
measure area and volume. Thus a square metre and a cubic metre appeared.
The main advantage of the system is that for shorter measurements
the metre is divided by ten, so a decimal system was used. Shorter units
had Latin prefixes and longer ones – Greek prefixes. So, ‗millimetre‘ is
Latin for ―a thousandth part of a metre‘ and ‗ kilometre‘ is Greek for ‗ a
thousand metres‘
As for the unit of mass, it was defined as the mass of a cubic centimeter of water at the temperature of 4°C (the temperature of its maximum density). As we know, the name of this unit is gramme.
The SI units is derived from the metric system and was internationally accepted in 1960. Besides metre (m), kilogram (kg) and
seconds (s), its basic units are Kelwin (K), ampere (a), mole (mol), and
candle (cd). This system was introduced in our country in the 1960s and
every day we measure things by the units from this system.