The fiction is b because the terms mean subtract
Sodium is a very reactive metal. It is kept in kerosene to prevent it from coming in contact with oxygen and moisture. If this happens, it will react with the moisture present in air and form sodium hydroxide.
The most distant planet is pluto
Answer:
Both are only physical changes.
Actually, sewing an apron and dust settling out of air are both physical changes, as an apron could be unseweed by cutting the thread used, and when we disturb the dust particles, the dust particles will fet mixed back in the air so both are physical changes.
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Exact numbers need not be measured. They can be counted. Conversion factors and countable units come under exact numbers. Measured quantities are measured using a device.
1) Number of microseconds in a week -Exact as it need not be measured. It can be estimated using the conversion factors between microseconds, seconds, minutes, hours, days and week.
2) Number of inches in a mile - Exact number as it is an established conversion factor.
3) The mass of a paper clip - Measured number as it has to measured using a weighing balance.
4) The number of pages in a book - Exact number as it is not measured. It can be counted.
5) Surface area of the dime-Measured number as it has to be measured.
6) The number of ounces in a pound-Exact number as it is a constant value.
