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Key Point: Set of numbers: {10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20}.
What are we learning? Counting from Ten to Twenty means saying, reading and writing the numbers 10, 11, 12, … up to 20. These numbers are just after 9 and before 21.
Number list and names:
How to understand these numbers:
Place value idea (simple): Numbers from ten to twenty can be seen as 1 ten and some ones. For example, 14 has 1 ten and 4 ones.
Tips to learn:
Key Point: For 10–19: N = 10 + r, where r is the number of ones (0 ≤ r ≤ 9). Example: 14 = 10 + 4.
Numerals are symbols we use to write numbers (for example, 10, 11, 12). Number names are the words we use to say those numbers (for example, ten, eleven, twelve). In the range 10–20 each number has a numeral and a name.
List of numerals and names (10–20):
Place-value idea (simple): numbers from 10 to 19 have 1 ten and some ones. For example, 14 has 1 ten and 4 ones. Twenty (20) is 2 tens and 0 ones. We can write this as tens + ones.
How to read and write: look at the numeral and say or write its name. For 11 and 12 remember the special spellings 'eleven' and 'twelve'; from 13 onward we use the base word + 'teen' (thirteen, fourteen, ... nineteen). Use objects (blocks, beads, counters) to show one group of ten and the extra ones.
Comparing numbers: first check how many tens a number has (1 ten vs 2 tens). More tens means a bigger number (so 20 > 19). If tens are same (both have 1 ten), compare ones: e.g., 18 > 15 because 8 ones > 5 ones.
Counting forward and backward: start at 10 and count to 20 (10, 11, 12, ..., 20). Successor of a number is one more (successor of 14 is 15). Predecessor is one less (predecessor of 14 is 13).
Key Point: Number = (tens × 10) + ones
What is place value? Place value tells us the value of each digit in a number depending on its position. For numbers from 10 to 20 we use two places: tens and ones.
Tens: A 'ten' is a group of 10 units. The tens place shows how many groups of ten are in the number.
Ones: The ones place shows the single units left after making groups of ten.
Reading a two-digit number (10–20): Look at the first digit (left) to find tens and the second digit (right) to find ones. Example: 14 means 1 ten and 4 ones. We can write 14 as 10 + 4.
Expanded form: Show a number as tens × 10 plus ones. Example: 17 = (1 × 10) + 7.
Visual idea: Use a ten-rod (a stick or strip of 10 cubes) to show each ten, and single cubes or dots to show ones. For 12, show one ten-rod and two single cubes.
Extra notes: Numbers that end with 0 (10 and 20) have 0 ones. So 20 = 2 tens and 0 ones (2 × 10 + 0).
Key Point: For 10–19: Number = 10 + ones (example: 14 = 10 + 4).
Representation with objects and pictures helps young children see what numbers mean. For numbers from 10 to 20, we show a group of ten and then some extra single objects. This makes it easy to understand that, for example, 14 is a full group of ten plus 4 more.
Ways to represent numbers 10–20:
Teaching tips: Always start with real objects, then move to pictures and written numerals. Encourage children to say the number as "ten and four" or write it as 14 after they build it with objects.
Key Point: For 10 ≤ N ≤ 19: N = 10 + (N - 10). Example: 15 = 10 + 5.
What it means: Composition of a number means making a number by putting smaller numbers together (adding). Decomposition means breaking a number into two or more parts (subtracting or splitting). For numbers from 10 to 20, we often show them as one ten plus some ones.
Place value idea (simple): Every number from 10 to 19 has 1 ten and some ones. We write: Number = 10 + ones. For example, 14 = 10 + 4. This helps children see numbers as a group of ten and extra ones.
How to teach it:
Simple rules children should learn:
Key Point: Next number = n + 1
A number line is a straight line with numbers placed at equal distances. It helps children see the order of numbers and do simple adding and subtracting. For Class 1 (numbers from ten to twenty) we draw a horizontal line, make small equal marks (ticks) and write numbers 0, 1, 2 ... up to 20. We often highlight the section from 10 to 20 for this chapter.
How to use it:
Drawing tips: Use equal spacing for ticks, label every number clearly, and use colors or dots to show start and end points when demonstrating addition or subtraction. For young learners, make the line large and interactive (floor tape or a long poster) so they can hop or place markers.
Key Point: Before n = n − 1
What it means
When we count numbers in order, each number has a number that comes just before it (called the before), a number that comes just after it (called the after), and sometimes numbers that come in the middle (called the between).
Numbers from 10 to 20
Every number from 10 to 20 can be shown as tens and ones. For example, 14 = 1 ten and 4 ones. To find the number before, we take one away. To find the number after, we add one.
How to find:
Tips for children
Key Point: a > b means a is greater than b (e.g., 16 > 12).
What it means: Comparing numbers tells us which number is greater, smaller or if they are equal. Ordering numbers means arranging them from smallest to largest (ascending) or largest to smallest (descending).
Numbers from 10 to 20 — a simple rule: All these numbers have the same tens digit (1). So to compare two numbers between 10 and 20, look at the ones digit (the second digit). The number with the larger ones digit is the greater number.
Signs we use:
How to compare — step by step (easy method for 10–20):
Using objects and pictures: Make groups of objects (e.g., 13 apples and 16 apples). Count the ones; the group with more objects is greater. Use ten-frames or a stick of ten plus extra counters to show numbers visually.
Ordering numbers: To order a list of numbers between 10 and 20, either:
Key Point: Even numbers = 2 × n (where n is a whole number). Example: 12 = 2 × 6.
Even and odd numbers tell us whether a number can be split into equal pairs. For the numbers from 10 to 20:
Pairing method: Put objects in groups of two. If every object has a pair and none is left alone, the number is even. If one object is left without a pair, the number is odd. For example, 10 stones make 5 pairs (even). 11 stones make 5 pairs and 1 single stone (odd).
Last-digit rule (easy check): If a number ends in 0, 2, 4, 6 or 8 it is even. If it ends in 1, 3, 5, 7 or 9 it is odd.
Number line idea: Start at 10 and jump by twos: 10 → 12 → 14 → 16 → 18 → 20 (all even). Start at 11 and jump by twos: 11 → 13 → 15 → 17 → 19 (all odd).
Key Point: If units add to less than 10: a + b = (units sum) with no carry (e.g., 4 + 3 = 7).
This topic teaches children how to add and subtract numbers up to 20 by using 10 as a helper number. The main idea is to "make ten" when adding (so one part reaches 10 and the rest is added) and to "use ten" when subtracting (so we break numbers around 10). Making ten helps children do sums that cross the ten barrier (for example, 8 + 5 or 9 + 7) and makes subtraction from numbers above 10 easier (for example, 13 − 5).
How to use the method:
Why it helps: Ten is the base of our number system, and making ten turns harder calculations into easy steps (work to 10, then add or subtract the small remainder). Using simple pictures (ten-frames, rods + units, number lines) makes the steps clear and concrete for Class 1 children.
Real-life contexts (brief): adding toys, sharing candies, counting fingers and toes, taking away pencils from a box of 10 + some.
Key Point: Next number = current number + 1 (e.g., after 14 comes 14 + 1 = 15).
Patterns are things that repeat or follow a rule. In the chapter Numbers from Ten to Twenty we look at number patterns using the numbers 10, 11, 12 ... up to 20. Children learn to see how numbers increase or decrease, repeat, or change in steps, and how tens and ones make each number.
Common patterns with 10–20:
How to continue a pattern: find the rule. If the rule is "add 1", then after 14 comes 15. If the rule is "add 2", after 14 comes 16. If it alternates (10, 11, 10, 11) the next will be 10 then 11 and so on.
Simple classroom exercises: fill in the missing numbers (10, __, 12, __, 14), circle even numbers between 10 and 20, draw 1 ten and the correct number of ones for a given number, continue the pattern, make your own repeating pattern using colors and numbers, and arrange objects in groups to show numbers from 10 to 20.
Teaching tip: use real objects (fingers, blocks, beads), a number line, ten-frames and colored cards to show and practice the patterns. Encourage children to say the rule ("+1", "-1", "+2", "alternate") out loud before filling answers.