Pebbles in a tin
A tin and some pebbles. You can use the glass pebbles that are used in vases of flowers. You need two different sizes of pebbles.
What other resource could I use to the same effect instead of pebbles?
Having taught maths to children from EYFS up to Y6, I felt that their mental maths skills were not always as well developed as they should be. Lower down the school children are often reliant on using fingers or counting equipment to add and subtract and the older children often use written formal methods unnecessarily. I wanted to encourage them to develop their ability to use mental calculation.
What I did
I got hold of a tin and some pebbles. In Reception, I told the children that I was going to drop some pebbles into my tin, one at a time, and I wanted them to count the pebbles as I dropped them. The children then had to show me how many pebbles were in the tin, using number fans which meant that they had to match the spoken number with the written symbol
I then took the pebbles out of the tin and dropped them in again, and we counted out loud to check what the total was.
Once the children were secure with counting the pebbles as they were dropped into the tin, I was able to move on to developing their ability to count on. I would drop, for example, 3 pebbles into the tin and we would all agree that there were three in there. I would then say,’ now I am going to drop in one more. How many are in the tin now?’ Another version of this was to drop some pebbles into the tin and say ‘now I am going to take one out, how many are in the tin now?’
After these activities, I would always reinforce the concept by showing what happens visually, using the pebbles, or pointing to the number line.
The tin of pebbles can be used further up the school too.
In Year 1:
- I told the children that each pebble was worth 2. I used the same ideas as in Reception, but this time, the children had to count up and back in twos.
- I used the pebbles to develop number bonds for 10. I did this by dropping, for example, 3 pebbles in the tin and asking the children how many more I needed to make 10.
- I introduced two different sized pebbles. The big ones were worth ten and the children had to count up and back in multiples of ten.
In Year 2:
- I used the pebbles to develop the children’s understanding of place value. Using the big and the small pebbles (tens and ones), I dropped, for example, 3 tens and 2 ones into the tin and asked what the value was in the tin.
- I then developed their ability to add or subtract multiples of ten from any two digit number by dropping e.g. 4 tens and 2 ones into the tin and agreeing that was worth 42. I then dropped in another ten (or more than one ten) and asked what the value was now. The same was done with subtraction by taking a ten out. Again, I always reinforced this concept by pointing to a hundred square or looking at the pebbles to see if the answer was correct and why.
In Key Stage 2 I used the pebbles to develop the children’s ability to count up and down in regular steps and improve their times tables. Before I dropped the pebbles in, I would tell them what the value of the pebbles is e.g. each pebble is worth 8. Then as I drop them in, the children have to count up in eights for example, 6 pebbles worth 8 each is 48.
I also ensured that they used the related division facts by saying to them, ‘if the value in the tin is 48, how many pebbles are in there?’
Higher up in Key Stage 2 I did the same activities but assigned decimal values to the pebbles.
I have found that this activity works well with all ages and abilities. It’s a very good way to start any lesson as the children are encouraged to sit silently in order to hear the pebbles as they are dropped into the tin. By using the number fans, all children are able to participate and it is easy for the teaching assistant to support lower attaining children by pointing to a number line or a hundred square as the pebbles are dropped in. It is also easy to extend the higher attaining children by asking them questions such as ‘what would the value be if I doubled (or halved) the number of pebbles in the tin?’ ‘How many more pebbles would I need to make x amount?’
By encouraging the children to count on or back in their heads, they all improve their ability to use mental calculation.
This is then reinforced by checking the answer by taking the pebbles out of the tin again and counting together or using visual aids such as a number line or a hundred square.