Three- and four-digit numbers · Usually met around P2
Estimating larger amounts
Count one part, then see how many parts.
How to do it
Method
Count one part, then see how many parts
12 in a box, 5 boxes → about 60
Another way
Groups of ten
6 groups of ten → about 60
In full
When there are too many to count one by one, count one small part, then see how many parts like it there are. One box has 12, and there are 5 boxes about as full, so there are about 5 twelves: 12, 24, 36, 48, 60, about 60. Or use something you know as a guide: a small jar holds about 20 sweets and the big jar holds about 4 small jars, so about 80. An estimate is “about”, not exact, but it must make sense: never fewer than one part, and not ten times too many. Or ring groups of ten, count the groups, then the rest.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
Every box in the picture holds about the same number of things. About how many are there in all the boxes?
Show the answer and working
Answer: 100
The first box has 25; there are 4 boxes, so add 25 4 times: about 100.
Example 2
A small jar holds about 50 sweets. A big jar holds about as much as 3 small jars. About how many sweets does the big jar hold?
- A. 150
- B. 50
- C. 53
- D. 1500
Choose the right answer
Show the answer and working
Answer: A. 150
The big jar is about 3 small jars of about 50: about 150.
Example 3
Without counting one by one, about how many 🎈 are in the picture? Choose the closest.
- A. 170
- B. 700
- C. 7
- D. 70
Choose the right answer
Show the answer and working
Answer: D. 70
10 in a row: count the rows and look at the last one: about 70.
Practise it in the game →Three- and four-digit numbers · Free to start, unlimited questions, no download