Читать книгу The Physics and Technology of Diagnostic Ultrasound: A Practitioner's Guide - Robert Gill - Страница 15

It is easy to make a mistake when making calculations. It is therefore strongly recommended that you do "reality checks" whenever you can.

One way to do this is to look at your final answer and see if it seems right. You will learn, for example, that typical ultrasound wavelengths are in the range 0.1 - 1.0 mm. Thus, if you are calculating a wavelength and get an answer of 25 cm you will know that something is wrong and the calculation needs to be checked.

You can also check the accuracy of calculations themselves. As mentioned above, the use of scientific notation separates the task of the numerical calculation from that of keeping track of powers of 10. It is usually possible to do an approximate check of the numerical part of the calculation by mental arithmetic to compare with the answer you have calculated using your calculator.

In the first example in the section on scientific notation above you can approximate the calculation on the second line as (6 × 7 × 2) ÷ 3 which gives 28. You can therefore see that the answer from the calculator (23.9) is in the right ballpark.