Numbers to 100 · Usually met around P1
Estimating how many
See one group of 10, then how many groups.
How to do it
Method
See one group of 10, then how many groups
About 4 rows of about 10 → about 40
Another way
Estimate, then count
Guess 40, count 38: close
In full
Estimating means saying roughly how many without counting them one by one. First see how big a small group is (a row of 10, say), then see roughly how many groups like that there are: about 4 groups means about 40. The answer only has to be close; from a few answers, choose the closest. Afterwards you can count them one by one to check how far off you were.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
Ka-yee lays some beans out in 4 rows of about the same length, with about 10 in each row. About how many beans are there?
Show the answer and working
Answer: 40 beans
About 10 a row; counting in tens 4 times: about 40.
Example 2
Estimate: there are more than 50 🎈 in the picture.
True or false?
Show the answer and working
Answer: True
10 to a row; look at the rows: there are 65.
Example 3
Tsz-ching estimates there are 56 🐟 in the picture. Count them: which is true?
- A. Tsz-ching's estimate is exactly right
- B. Tsz-ching's estimate is too many
- C. Tsz-ching's estimate is too few
- D. You can't compare without counting
Choose the right answer
Show the answer and working
Answer: B. Tsz-ching's estimate is too many
Counted one by one there are 45; then compare 56 with 45: tens first, then ones if the tens match.
Practise it in the game →Numbers to 100 · Free to start, unlimited questions, no download