Why 200 + 10% is not 220 on this calculator
Scientific calculators evaluate expressions. Their percent key need not behave like the contextual percent key on a shopping calculator.
Scientific calculator →Percent is an operation
Here, x% means x/100. Consequently 200 + 10% is 200 + 0.1 = 200.1. To increase 200 by 10%, enter 200*(1+10/100), giving 220. To take 10% of 200, enter 200*10/100, giving 20. Writing the full expression also makes the intention easier to review later.
Grouping changes the answer
Multiplication is evaluated before addition, so 2+3*4 gives 14. Parentheses make (2+3)*4 equal 20. When a fraction has a multi-term numerator or denominator, enclose each part: (8+4)/(2+1) gives 4. Do not assume a long expression is evaluated from left to right as it is entered. Explicit multiplication also avoids ambiguity between a number and a following parenthesis.
Check before trusting the display
Estimate the magnitude before pressing equals. A 10% increase should be slightly larger than the starting amount, not 10 times larger. Division by zero, a real square root of a negative value, or an overflowing factorial does not yield a usable result. Correct the mathematical input rather than repeatedly pressing equals. Use the dedicated percentage or discount calculator when you want labeled inputs instead of an expression. For repeated work, copy the complete expression into your notes so its base and grouping remain visible when reviewing results.
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