Percent call relative units in which some share from the general whole is expressed, divided into hundred equal parts. As it is relative unit, it gives the chance to compare incomparable, apparently, measurements - for example, it is possible to compare a difference between milk yield of the Australian and Norwegian Burenkas to a difference in number of sunny days in these countries. Calculation of a percentage difference of two indicators - operation not the difficult, but having some features.
Instruction
1. Before starting calculations, find out which of numbers should be taken for 100%, i.e. define "a basic indicator". Let's say in conditions weight characteristics of components of rocket fuel are given: 6 tons of kerosene and 4 tons of oxidizer. Then it is possible to take the total weight (10 tons) for 100%, it is possible to compare amount of oxidizer concerning kerosene (100% = 6 tons), and it is possible to take for a basic indicator oxidizer weight (100% = 4 tons). In each case the percentage expression of a difference between reference values in relative units will give different sizes.
2. Use the basic indicator defined in the first step to find out, how much? percent is the share of each absolute unit. Let's tell if in the example given above the total weight (6+4=10) was taken for 100%, then 100/10=10 relative units (percent) will fall on each absolute unit of measure (ton). If oxidizer weight is taken for a basic indicator, then to each ton there will correspond 100/4=25% and if kerosene - 100/6≈16.67%.
3. Find a difference between the compared sizes in absolute units. This value does not depend on a basic indicator and is defined by usual operation of subtraction. For the example used above what you took for hundred percent, the difference will be equal to two tons, but when comparing concerning kerosene this size will be negative: 4-6=-2.
4. Transfer a difference of absolute values (tons) to relative units (percent). For this purpose increase the number received on the previous step by the value received on the second step. In our example it means that the difference of weight of components in tons (2) should be increased by the number of percent falling on each ton. If the total weight of fuel was taken for a basic indicator, it is necessary to multiply by 10%: 2*10%=20%. If comparison is carried out concerning oxidizer weight, then the multiplier has to be equal to 25% (2*25=50%) and if a basic indicator - the weight of kerosene, then 16.67% (-2*16.67=-33.34%).
5. If necessary to present a formula of calculations in a general view designate initial sizes, for example, by the letters X and Y, and a percentage difference - letter p. Then the formula of calculations concerning the sum of reference values will look so: p= | X-Y | *100/(X+Y). For calculations concerning variable X this formula should be changed so: p=(Y-X) * 100/X, and concerning variable Y a formula will be such: p= (X-Y)*100/Y.