Plain-English guides for the calculations that come up more than you would expect.
The formula is (Part / Whole) x 100. Three types, worked examples, and the mental tricks for 10%, 15% and 20%.
Read →Subtract the birth year from the current year, then subtract one more if the birthday has not happened yet this year. Formula and examples.
Read →Subtract the earlier date from the later one. How to do it by hand, in Excel, and why months and February make it messier than it looks.
Read →Divide the numerator by the denominator. 3/4 = 0.75, 5/8 = 0.625. Reference table and the reverse included.
Read →Sale Price = Original Price x (1 - Discount%). Twenty percent off $80 is $64. Worked examples for common discount rates.
Read →Seven letters, one subtractive rule, no zero. How the system works and a quick conversion chart.
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