The percent designates a one hundredth part of any quantity. Therefore addition of percent, in principle, differs in nothing from addition of ordinary numbers. However at the same time it is necessary to watch closely that all composed percent belonged to the same quantity. Otherwise, at addition of percent it is very easy to be mistaken.
It is required to you
- - calculator;
- - computer.
Instruction
1. To put percent from a certain number, just put the number of all percent. The total number of percent will also be the sum of percent for this number. Pay special attention to that the number from which percent are considered in a statement of the problem remained to constants.
2. Example: From the salary of the employee 13% of income tax, 1% of trade-union collecting and 25% of alimony were withheld. What general percent of deduction from the salary of the employee? Decision: 13% + 1% + 25% = 39%.
3. If in the course of calculation of percent the initial quantity changes, then surely consider these changes. In each case it is necessary to consider the features of the decision – sometimes, absolutely unobvious.
4. PrimerCherez half a year after acceptance for work the salary of the employee was increased by 10%, and then, in half a year, for 10%. By how many percent did the salary of the employee for all year increase? ReshenieObychnyy addition of percent will yield result of 20%. Check – whether so it actually. Let initial salary was H. Togd, after the first increase its size will be: X * (100%+10%)/100 = 1.1*X. After the second increase the amount of salary will be: 1.1 * X * (100%+10%)/100 = 1.21 * H. Itak, the amount of salary increased by 1.21 times that is equivalent to increase by 21%.
5. Sometimes the divergence between the obvious and correct decision at addition of percent can reach hundreds of percent. Therefore it is necessary to analyze statements of the problem attentively.
6. Primerv shop brought ton of cucumbers with humidity (water content) of 99%. For storage time the humidity of cucumbers decreased by 1%. What did the humidity of cucumbers and by how many percent their weight decreased become equal to? ReshenieNahozhdeniy a new indicator of humidity it is obvious (and it is correct): 99% - 1% = 98%. And here the arising way of determination of mass of the "dried-out" cucumbers of 1000 kg * 0.98 = 980 kg in principle is incorrect. The problem is that 98% need to be calculated from the new mass of cucumbers which weight just and is required to be determined. In similar cases you make calculation from any invariable size. For example, for cucumbers it is possible to enter a conditional concept of "the dry rest" (even if culinary specialists will begin to be indignant). So, the mass of the dry rest in fresh cucumbers was: 1000 kg * 1% = 1000 * 0.01 = 10 kg. Let's designate through the X mass of the "dried-out" cucumbers. As the mass of the dry rest did not change, but began to be 2%, it turns out: X (kg) * 2% = X * 0.02 = 10 kg, from where X = 500 kg. Therefore, the weight of cucumbers decreased by 50%. By the way, if the return problem (the humidity would increase from 98% to 99%), then change of weight would be 100% was solved.