Identify, represent, and estimate numbers using different representations including the number line
You already know the digits in a number and how to show it with objects. A number has even more ways to look: a spot on a number line, a place-value chart, or a quick drawing. They all mean the exact same number.
Zara has the number 346. She shows it with base-ten blocks: 3 hundred-flats, 4 ten-rods, and 6 ones cubes. She also finds its spot on a number line zoomed in near 340 to 360. Then she draws 3 big squares, 4 lines, and 6 dots. All three show the same number, 346.
A place-value chart is a row of columns with names on top: hundreds, tens, ones. Each digit gets its own column. In 264 the 2 goes in the hundreds column, the 6 goes in the tens column, and the 4 goes in the ones column. If there is nothing for a column, write 0 there so the other digits stay in their own spots.
Sometimes you do not need the exact number. An estimate is a close guess that is quick to make. Look at a group you already know, like a jar of 10 or a jar of 50, then compare it to the new group. You can estimate on a number line too. A mark between the 30 and 40 ticks is in the thirties, and a mark sitting halfway between them is about 35.
Two things are easy to slip on. First, watch the size of each block: a ten-rod is worth ten, not one, so counting every block as a single thing gives a number far too small. Second, when you hunt for a number on a line, read its tens digit first, because that digit tells you which pair of ten marks the number sits between. A number with 9 tens sits up near the top of a 0 to 100 line, nowhere near the 1.
The same number can be blocks, a number line spot, a drawing, or place-value columns, and you can estimate 'about how many' without counting one by one.
You know each digit's job: the hundreds spot, the tens spot, the ones spot. Zara has the number 346. She is building it out of base-ten blocks. So far she has put out 3 hundred-flats and 6 ones cubes.
How many ten-rods does Zara still need?
Jobs that lean on this skill. Follow one to see everything it is built on.
33 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.