For example, if I have the number 3.78 and want to round it to the nearest tenth (which means showing only one digit after the decimal), we look at the last digit (the 8) and see that it’s greater than or equal to 5. Since this is true, we “round up” by adding a 1 to the previous digit (3) and keeping the same last digit (8). So our rounded number would be 3.8!

Now let’s say I have another number, like 4.26. If I want to round this to the nearest hundredth (which means showing two digits after the decimal), we look at the second-to-last digit (the 6) and see that it’s less than or equal to 5. Since this is true, we “round down” by keeping the same previous digit (4) and changing the last digit to a 2 instead of a 6. So our rounded number would be 4.26!

As for controlling decimal precision, that’s just a fancy way of saying how many digits after the decimal point we want to show or use in calculations. For example, if I have two numbers like 3.14 and 0.57, and I only care about showing one digit after the decimal (which is common when working with money), then I can round both of those numbers down to just their whole number parts: 3 and 0!

But what happens if we want to use more than one digit after the decimal point? Let’s say we have a calculation that involves multiplying two decimals together, like this: (1.25 * 4.76). If we only care about showing two digits after the decimal in our answer, then we can round both of those numbers down to just their whole number parts before doing the multiplication: (1 * 4) = 4!

But what if we want to show more than one digit after the decimal point? Let’s say we have a calculation that involves dividing two decimals together, like this: (25.67 / 3.89). If we only care about showing three digits after the decimal in our answer, then we can round both of those numbers down to just their whole number parts before doing the division: (25 * 10) = 250 and (3 * 10) = 30!

It can be helpful for simplifying calculations, especially when working with money!