1Units get different names for different sizes
The same length can be written in mm, cm, m, or km depending on the situation. It's just much more convenient to use mm for something tiny, and m or km for something as big as a room or a playing field.
Weight works the same way. Small objects are measured in g, and people or heavy loads are measured in kg.
2Units convert by fixed multiples
Changing units doesn't change the real size — only the number you use to count it changes.
1L = 1000mL and 1kg = 1000g work the same way.
On the activity page, moving the slider changes the values of all four units at once. Watch how the number changes, but the actual size it points to always stays the same.
3Estimating starts with a "reference object"
Once you know a carton of milk is 200mL, you can guess right away that a 2L bottle is "about 10 milk cartons' worth." Using one familiar object as a reference makes it much easier to estimate the size of something you've never seen before.
How many cm long is your pinky finger? How many mL is the water bottle you drink from every day? Knowing a few of these makes estimating easy anywhere.
4Estimating is a sense, not an exact calculation
There isn't just one "correct answer" for an estimate. If your guess falls in a range close to the real value, you estimated well. That's why the estimating quiz asks you to pick "about this size" rather than an exact number.
5Try playing like this
- Switch tabs and compare. Move between the length, volume, and weight tabs and see how the same slider move shows up differently for each unit.
- Guess using things around you. Before checking the quiz answer, guess for yourself first, then see if you were right.
- Build a list of reference objects. Picking one object you know well for length, volume, and weight will help a lot the next time you estimate.