Estimating Calculations
Maths: Year 3 & 4 National Curriculum, topic 1.2.3
Estimation
Estimation is when we try to think about the size of an answer to a number problem before we have fully worked it out. Estimation helps us to decide if our answers make sense.
Easier numbers
- Which calculation is easier:
- 396 + 512 = ?
- 400 + 500 = ?
- Most people would find the second calculation easier because it uses a simple number fact:
- 4 + 5 = 9, so 400 + 500 = 900.
Near numbers
- Did you notice that 396 was near to 400 and 512 was near to 500?
- To estimate 396 + 512 we can use the near numbers 400 and 500 because they are easier to calculate.
Checking
- The actual answer to 396 + 512 is 908:
- 396 + 512 = 908
- We see that the answer is close to our estimation.
- That means we can use estimation to check our answers.
Test yourself on Estimating Calculations
What is the near number for 321?
What is the near number for 973?
Which addition gives an answer with a near number of 1000?