An estimate is a sensible guess made before measuring.
Estimate is a careful guess, close to the real answer.
Step 1: Let's Learn
Read it, or press Listen and follow the words.
Use something you know
Your fingernail is about 1 centimetre. Your thumb is about 1 inch. A big step is about 1 metre.
How to estimate
Picture the known length, then ask how many would fit along the object.
An estimate does not have to be right. It has to be close.
Estimating means comparing, not guessing
A wild guess and an estimate are different things. An estimate starts from something whose size you already know. If you know your hand is about 15 centimetres across, and a book looks about two hands wide, your estimate is about 30 centimetres. The known thing is called an anchor.
Estimate first, then measure
Always make the estimate before you pick up the ruler. If you measure first, your "estimate" is just the answer repeated back. Estimating first and then checking is how your sense of size actually improves — you find out which way you tend to be wrong.
What counts as a good estimate
An estimate does not have to be right. It has to be close and it has to be fast. If a pencil is 14 centimetres and you said about 15, that is a good estimate. If you said about 40, that is worth thinking about — your anchor may need adjusting.
Step 2: Try It Yourself
Tap and try it out.
centimetres
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It starts at 0 and ends at 7, so it is 7 centimetres long.
Step 3: Watch an Example
One step at a time.
Watch Ana Estimate
Ana is asked to estimate the length of her rubber in centimetres.
- Step 1
She pictures her fingernail, which is about 1 centimetre.
Step 4: Your Turn
Practice makes it stick.
The Door
Problem 1 of 2
About how tall is a classroom door?
The Spoon
Problem 2 of 2
About how long is a teaspoon?
Sensible or Silly?
1 of 3
A pencil is about how long?
2 of 3
A bus is about how long?
3 of 3
About how many centimetres wide is your fingernail?
Step 5: Quick Check
Show what you know.
Question 1 of 2
About how long is one big step?
Question 2 of 2
Does an estimate have to be exactly right?
What You Learned
- An estimate is a careful guess before measuring.
- Use a length you know: a fingernail, a thumb, a step.
- Close is good enough for an estimate.