Counting 1 to 100

1Summary 重點摘要

Tens are groups of ten, e.g. 30 is three tens.

2Vocabulary cards Vocabulary

3Step by step Steps

1. Step 1: Tens make decadesWhen there are many things to count, bundle the sticks in tens first; one bundle stands for one ten, and this makes counting fast and tidy. Example: 3 bundles of 10 sticks are 3 tens, which make 30, and 5 tens make 50. Count the bundles first to find how many tens a number has. Be careful: before counting, check that every bundle really holds 10 sticks; if one bundle has only 9 sticks but is counted as 10, the total will come out too big.
2. Step 2: Add the onesAfter bundling the tens, the loose sticks left over are the ones; only when tens and ones are put together is the number complete. Example: 3 bundles plus 5 loose sticks make 30 + 5 = 35. Count the tens first and the ones second, and the clear order keeps everything tidy. A common mistake is forgetting to add the loose sticks and answering only 30, or writing 30 and 5 together as 305; remember to count tens and ones separately, then join them.
3. Step 3: Place valueEach digit means something different depending on its place, and this is called place value. Example: in 35, the 3 is in the tens place and means 3 tens, which is 30, while the 5 is in the ones place and means 5 ones; together they make 35. If we swap the digits and write 53, the meaning changes completely. When writing or reading a number, start from the left, tens first and ones second; writing 35 backwards as 53 happens when the place of each digit is not watched.
4. Step 4: Ten tens make 100Ten tens joined together make a new counting unit: one hundred. Example: 10 bundles of 10 sticks are 10 tens, which make 100. When we count, the number 100 comes right after 99, so 100 holds exactly 10 tens. Note that 100 is a three-digit number: its 1 sits in the hundreds place followed by two zeros; writing 100 as 10 or as 1000 happens when we forget that the hundreds place takes the 1 and both the tens and ones places take 0.
5. Step 5: Count in tensWhen there are many things, we can skip-count in tens instead of counting one by one. Example: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100. Each time the tens digit grows by 1 while the ones digit always stays 0, so counting is fast and tidy. Practise counting to 50 first, then go on to 100 when you are ready. A common mistake is skipping one of the tens numbers, for example jumping from 40 straight to 60; before skip-counting, read the ten tens numbers in order once.
6. Step 6: Compare numbersTo compare two two-digit numbers, look at the tens digit first; the number with the bigger tens digit is larger, and only when the tens are equal do we compare the ones. Example: compare 47 and 74; 4 is less than 7, so 47 < 74. Another example: 68 and 65 both have 6 tens, so compare the ones; 8 is greater than 5, so 68 > 65. A common mistake is deciding by the ones digit alone and forgetting the tens, yet the tens place is the position that decides the size of two-digit numbers.

4Diagrams Diagrams

5Worked example Example

6Common mistakes Mistakes

7Quick check Quick check

8Recap Recap

• Tens make decades: 3 tens = 30.
• Place value: tens before ones.
• Ten tens make 100.
• Skip count: 10, 20, 30... 100.
• Compare tens first.