1
Eighteen
Discover Mathematics: Chapter 4
GoalCount, read and write 18, and use a class picture graph to find how many children there are in all.
New words
eighteen · ten and eight morein all · everything togetherclass · the children who learn together
Explanation
Eighteen is ten and eight more. On two ten-frames, eighteen is one full frame and eight counters on the second frame. Two squares of the second frame are still empty. Seventeen comes before eighteen and nineteen comes after it. In the numeral 18, the 1 is on the left and the 8 is on the right. To find how many children are in a class from a picture graph, count each row and then count all the pictures together.
Worked examples
Nour counts the palm trees along the road: 1, 2, 3, up to 18.
Two groups of 9 butterflies make 18 butterflies.
Here are 10 flowers and 8 more flowers. Ten and eight more is eighteen.
Class activity
Count a collection. Gather 18 small things, such as beans, in a bowl. Count 10 into one small cup and the rest into another. Say: ten and eight more is eighteen. Then take 1 away and say what number is left.
Practice
1
How many balloons are there?
18
2
How many counters are on the two ten-frames?
17
3
Salma’s class voted for a fruit. 8 children chose bananas, 6 chose oranges and 4 chose apples. How many children are in the class in all?
18
4
What is one more than 17?
18
5
What is one less than 18?
17