Rounding a number to a specific number of decimal places

I was working on a small app that needed to round some numeric values. For example, given a number such as 123.456789, I wanted to round this off to two decimal places such as 123.46. Why .46 instead of .45? Because the value is rounded at the n-th decimal place (.456 rounds up to .46).

MIT App Inventor does not have a function to do this sort of round off – well, not exactly. Actually, it has a formatting function that can accomplish the same thing but it is intended for converting numeric values to text strings.

I created a simple little program to demonstrate how this works, plus a couple of other methods to implement this feature.

Update: This post has been updated with thanks to Taifun for noting that App Inventor does have a “raise to a power function”. See below for more details and a link to his great web site!

User Interface View

The user interface prompts for a number, and the number of decimal places to which it should be rounded. Press the Round off number button to see the result.

RoundOffUIHere you can see that 123.4567 has been rounded to 123.457.

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