Question

How much less is 28 km than 42.6 km?

Answer 1

Hint: First look at the definition of measurement, units. Categorize given units into one type of all possible types. Use interrelation to find the value of a given unit in terms of another. Use the new found value in terms of other units to get the required result asked in the question.

Complete step-by-step solution -
Measurement: Measurement is assignment of a number to a characteristic of an object or events. The scope and application of measurements are dependent on the context and discipline. The measurement can be compared with other objects or events measurement do not apply to nominal properties of an object as an event.
Units of measurements: A unit of measurements is a definite magnitude of quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. Any other quantity of that kind can be expressed as a multiple of the unit of measurement. Unit is the point used in the process of determining how large or small a physical quantity is as compared to a basic reference quantity of the same kind. This basic reference is called SI, (which is an abbreviation for International system of units). There are seven SI base units, which are length(metre), time(seconds), amount(mole), electric current (A), temperature (kelvin), luminous intensity (candela), mass(kilogram).
Given measurement in the question can be written as:
28 km < 42.6 km. These come under length in types of units. The inter relation between km, m can be written in form of
$1\,km\,=\,1000m.................(i)$
By multiplying 28 on both sides, we get the equation:
$28\,km\,=\,28000m..............(ii)$
By multiplying 42.6 on both sides of equation (i), we get it as:
$42.6km\,=\,42600m…........(iii)$
Let us assume a measurement denoted by variable B in metre.
Let us say 42.6 km is B metre more than 28 km, we can also say that 28 km is B m less than 42.6 km.
So, we can write the above statement mathematically as:
$28\,km+B\,metre=42.6km$
By substituting equation (ii), (iii), we can write:
$28000+B=42600$
By subtracting 28000 on both sides, we can write it as:
$B=426000-28000=14600metre$
By multiplying 14.6 on both sides of equation (i), we get:
$14.6\,km=14600metres$
By this equation, we can say 28 km is 14.6 km less than 42.6 km.

Note: We converted into basic units in order to avoid the difference of decimals, alternating you can directly subtract 28 from 42.6km to get 14.6km. Be careful while converting, generating students forget about decimals and write 42.6km=426000m which is wrong. You must take care of the decimal point present in the question.