The operation is: $21.99 + 9.75$$\%$
On the Texas Instruments model TI36X-Pro the answer is: $22.0875$
But when I tried on the Casio FX-991ES Plus the result is: $24.134025$
Which is the correct answer?
And how these two calculators reach different results?
Best Answer
It depends on how we 'read' $21.99 + 9.75\%$
(1) As $\%$ is derived from the latin 'per centum' (which means 'out of one hundred'), we have $$ 9.75\% = \frac{9.75}{100} = 0.00975 $$ giving answer one.
(2) Many calculators allow the input
21.99 + 9.75%being a shortcut for the operation 'add 9.75% of 21.99 to the given 21.99', which is $$ 9.75\% \cdot 21.99 = 2.144025 $$ giving the second answer.If I should choose the 'correct' one, this would be (1), but the better way is not to use notation like that.