Two digit number divisible by 9 if the tens digit is twice the ones digit

In 2-digit numbers, there are only two place values - the units place and the tens place. Every number which has more than 1-digit has different digits described by their place values. 2-digit numbers start from 10 and end on 99. In other words, the smallest 2-digit number is 10 and the greatest 2-digit number is 99.

What are 2-Digit Numbers?

2-digit numbers are the numbers that have two digits and they start from the number 10 and end on the number 99. They cannot start from zero because in that case it will be considered as a single-digit number. The digit on the tens place can be any number from 1 to 9. For example, 45, 78, 12 are two-digit numbers.

Place Value in 2 Digit Numbers

Place value is the position of each digit in a number. When we talk about 1-digit numbers there is only one place value that is the ones place. When we come to 2-digit numbers, there are two place values - ones and tens. Observe the following figure which shows a two-digit number 23 written along with its place values. The digit 2 is at tens place and stands for 20 and digit 3 is at ones place and stands for 3.

Assigning Place Values

We know that the place value of a number tells the position of the digit. In 2-digit numbers, tens and ones are the only place values.

Let us look at the following set of numbers to understand the combination of ones and tens:

a.) 33 ⇒ 3 tens + 3 ones = (3 × 10) + (3 × 1) = 30 + 3 = 33

b.) 18 ⇒ 1 tens + 8 ones = (1 × 10) + (8 × 1) = 10 + 8 = 18

c.) 27 ⇒ 2 tens + 7 ones = (2 × 10) + (7 × 1) = 20 + 7 = 27

How to Write Numbers up to 2-Digits?

2-digit numbers can be written in the numeral form, in words, and in the expanded form. For example, 45 is a 2-digit number. Let us see the three ways in which it can be written.

• In the numeral form: 45
• In words: Forty-Five
• In the expanded form: 40 + 5

2-Digit Numbers in Words

When numbers are written in words with the help of the place values, it helps us to spell them. The smallest 2-digit number is 10 which is written as ten. After this, the numbers from 11 to 20 are written as 11 - eleven,12 - twelve, 13 - thirteen, 14 - fourteen, 15 - fifteen, 16 - sixteen, 17 - seventeen, 18 - eighteen, 19 - nineteen, and 20 - twenty. After this, they are written as 21 - twenty-one, 22 - twenty-two, 23 - twenty-three, and so on till it reaches 30 - thirty, and the same pattern is followed after thirty, forty, and so on.

2-Digit Numbers in Expanded Form

The expanded form of a number helps to know about its constituents. The expanded form of a 2-digit number can be shown in different ways. Consider a 2-digit number 57.

• The number 57 can be written in one form as 57 = (5 × tens) + (7 × ones)
• In another way, it can be written as 57 = (5 × 10) + (7 × 1)
• The third way to write 57 in the expanded form is 57 = 50 + 7.

Common Mistakes of Numbers up to 2-Digits

• Children can often recite all numbers up to 99 (or 100) but may make mistakes when asked to find a larger number between two numbers. They recite numbers from 1 to 100 like they have memorized the letters of the alphabet. If this happens, then finding the greater number between 14 and 15 is as puzzling as finding the greater letter between C and D. Children must realize that, unlike letters, numbers have a relationship with each other. 15 is exactly one more than 14. For this, number lines and color counters can be used to associate the sound with the quantity.
• Children tend to make mistakes working with numbers when the tens place value changes. For example, when going from 19 to 20, 29 to 30, 39 to 40, etc. Often 2-digit numbers are introduced without reference to place values. While this makes it easier to memorize numbers, it may not be the best strategy as children don’t see numbers as constructed from a common set of digits from 0 to 9. In this case, an abacus can be used to model numbers and Base-10 blocks can be used to help them visualize numbers.
• Children make errors in writing or reading numbers in words, especially from eleven to nineteen. There is no substitute to practice. Children must practice writing number names. Generally, with a little bit of deliberate and targeted practice, this error can be fixed easily.

Given below are some tips and tricks on numbers up to 2-digits.

• When any one-digit number (from 1 to 9) multiplies by 10 the resultant number is a 2-digit number. For example, 4 × 10 = 40
• The smallest 2-digit number, using only one digit is 11.
• The smallest 2-digit number, using two different digits is 10. (10 is the smallest two-digit number too)
• The greatest 2-digit number, using only one digit is 99. (99 is the greatest two-digit number too).
• The greatest 2-digit number, using all different digits is 98.
• There are only two place values in two-digit numbers, tens and ones.
• There are ninety, '2-digit numbers' starting from 10-99.

Here is the list of all Numbers up to 2 Digits from 10-99.

Smallest 2 Digit Number

The smallest two-digit number is 10 because the previous number is 9 which is a one-digit number.

Greatest 2 Digit Number

The largest 2-digit number is 99 because the next number is 100 which is a 3-digit number.

Important Notes

Given below are some important notes related to numbers up to 2 digits that we studied in this article.

• The smallest 2-digit number is 10 and the greatest 2-digit number is 99.
• There are ninety, 2-digit numbers in all.
• A 2-digit number cannot start with 0, because in that case it will be considered as a single-digit number.

☛ Related Articles

1. Example 1: What is the difference between the largest 2-digit number and the number 20?

   Solution: Largest 2 digit number = 99
   Difference between 99 and 20 is 99 - 20 =79

2. Example 2: Create a 2-digit number in which 7 is in the tens place and 5 is in ones place. Write the number in the expanded form and write its number name.

   Solution: If 7 is in tens place and 5 is in ones place, the number is 75. The expanded form of 75 = 70 + 5. This can also be written as (7 tens) + (5 ones), or, (7 × 10) + (5 × 1)

   The number name of 75 is seventy-five.

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FAQs on Numbers up to 2-Digits

A number is said to be a 2-digit number if it consists of two digits, in which the digit on the tens place must be from 1 to 9, it cannot start from zero because in that case, it will become a single-digit number. For example, 35, 45, 60, 11, and so on are 2-digit numbers.

How many Two-Digit Numbers are there?

There are ninety, 2-digit numbers in all, starting from 10 and ending on 99. This means that the smallest 2-digit number is 10 and the largest 2-digit number is 99.

What is the Largest 2-Digit Number?

The largest 2-digit number is 99 as the following number is 100 which is a 3-digit number.

What is the Smallest 2 Digit Number?

The smallest 2-digit number is 10 because the preceding number is 9 which is a one-digit number.

What is the Biggest 2 Digit Number Divisible by 10?

The biggest 2-digit number divisible by 10 is 90. Although the biggest two-digit number is 99, it is not divisible by 10.

What is the Largest 2-Digit Number that can be formed with 8 and 6?

The largest 2-digit number that can be formed using 8 and 6 is 86. Since 8 is greater than 6 that is why we keep 8 at tens place and 6 at ones place. Therefore, 86 is the largest two-digit number with digits 8 and 6.

Write the Expanded Form of the Given 2 Digit Number 65.

The expanded form of 65 is 60 + 5. This can also be written as, 6 tens + 5 ones, or, (6 × 10) + (5 × 1).

How many Tens are there in the 2-Digit Number 20?

In the given number 20, the digit 2 is at tens place. Therefore, there are 2 tens in 20. This can be written as 20 = 2 tens + 0 ones.

Can 2 Digit Numbers Start with 0?

No, 2-digit numbers cannot start with 0. The digit at tens place in a 2-digit number cannot be zero, it can be any number from 1 to 9, otherwise, it will be considered as a 1-digit number. For example, 05, 06, 07, are all 1-digit numbers, and 56, 78, 79 are all 2-digit numbers.

What are the Place Values in Numbers up to 2-Digits?

Place value helps in identifying the position of digits. There are only two place values in 2-digit numbers - tens and ones. For example, in the number 98, 9 is at tens place and 8 is at ones place.

Which is the Largest 2 Digit Prime Number?

The largest 2-digit prime number is 97 because 97 has only 2 factors, 1 and 97.