And now we're going to look at how we can estimate with fractions and decimals. So a triangle has sides of 3 and 1 fourth, 5.8, and 9 and 6 sevenths. Estimate the perimeter. First we'll set up our triangle so that we can see visually what it will look like. So we know that to find the perimeter of a triangle, we're going to add the lengths of all three sides together. But they tell us to just estimate the perimeter. So we don't need to find the exact value. So whenever we see the word estimate, remember that it means that we can round the numbers first and then calculate the answer. So let's see where all of these numbers would fall on a number line. That's going to help us to round them off. Here's a little number line, and we place all three of our numbers there. Notice that the 3 and 1 fourths is closest to the 3. We want to see what whole number each of these is closest to. We're going to round them off to whole numbers. So 3 and 1 fourths would round off to 3 because it's closest to 3 on the number line. The 5.8 is closest to the 6th, so that will round off to 6. And 7 and 8 ninths is closest to 8, so that will round off to 8. Now that everything is rounded to a whole number, we can add them up to find the perimeter. So we have 3 plus 6 plus 8, add those up, and we get 17. So now we know that the perimeter of the triangle is about 17.