TWO DIGIT NUMBERS -
STUDY OF NUMBERS 10 TO 99;
PLACE VALUE RULE

Learn/Teach
Two Digit Numbers
through Fun Math Games.
For details, see near
the bottom of this page.

Successor of a number :

The successor of a number
is 1 more than the number.

Predecessor of a number :

The predecessor of a number
is 1 less than the number.

To express counting of
quantities higher than
nine (9), we use the same
symbols and follow certain
mathematical rules that are
used to represent any number.

In the discussion on
Single Digit Numbers,
when one (1) chocolate was
added to the already present
nine (9) chocolates, we got
the successor to 9 and called
it ten and denoted it as 10.

Here, two of the symbols
(digits) from the set,
0 and 1 are used with a
mathematical rule.

The rule is the
place value rule.

The value of the right extreme
place is one (1) or unity.

Value of the place increases
as it moves to the left.

Value of the place becomes
ten times, as we move
one place to the left.

So

the value of the place second
from right is ten times one
and is equal to ten.

So 10 stands for zero ones
added to one ten which is ten.

To get higher numbers,
we use appropriate digits
in the appropriate places.

The successor to 10 is called
Eleven and is denoted by 11
( one one added to one ten.)

The names of subsequent numbers
and their notations are

twelve, 12
( two ones added to one ten.);
thirteen, 13
( three ones added to one ten.);
fourteen; 14
( four ones added to one ten.);
fifteen; 15
( five ones added to one ten.);
sixteen; 16
( six ones added to one ten.);
senventeen; 17
( seven ones added to one ten.);
eighteen; 18
( eight ones added to one ten.);
nineteen, 19
( nine ones added to one ten.);

The successor to 19 is called
twenty and is denoted by 20.
(see, the value is
zero ones added to two tens).

The names of subsequent numbers
and their notations are
twenty one, 21
( one one added to two tens.);
twenty two, 22
( two ones added to two tens.);
twenty three, 23
( three ones added to two tens.);
twenty four, 24
( four ones added to two tens.);
twenty five, 25
( five ones added to two tens.);
twenty six, 26
( six ones added to two tens.);
twenty seven, 27
( seven ones added to two tens.);
twenty eight, 28
( eight ones added to two tens.);
twenty nine, 29
( nine ones added to two tens.);

The successor to 29 is called
thirty and is denoted by 30.
(see, the value is
zero ones added to three tens.).

The names of subsequent numbers and
their notations are similar to the
set given above after 20. They are

thirty one, 31
( one one added to three tens.);
thirty two, 32
( two ones added to three tens.);
thirty three, 33
( three ones added to three tens.);
thirty four, 34
( four ones added to three tens.);
thirty five, 35
( five ones added to three tens.);
thirty six, 36
( six ones added to three tens.);
thirty seven, 37
( seven ones added to three tens.);
thirty eight, 38
( eight ones added to three tens.);
thirty nine, 39
( nine ones added to three tens.);

The next set is, forty denoted by 40 and
then forty one, 41 to forty nine, 49.

The other sets are
fifty denoted by 50 and then
fifty one, 51 to fifty nine, 59.
sixty denoted by 60 and then
sixty one, 61 to fifty nine, 69.
seventy denoted by 70 and then
seventy one, 71 to seventy nine, 79.
eighty denoted by 80 and then
eighty one, 81 to eighty nine, 89.
ninety denoted by 90 and then
ninety one, 91 to ninety nine, 99.

Example on Two digit Number

In the above example,
the value of 96
= 9 tens + 6 ones
= 90 + 6 = 96
It is written as ninety six.

The numbers discussed so far are
Single Digit Numbers, (0 to 9)
and two digit numbers (10 to 99).
Let us have an exercise on these
one and two digit numbers.

Exercise On Two digit Numbers

1. What is the predecessor
   number to 79 ?
2. What is the successor
   number to 59 ?
3. What is the number
   between 83 and 85 ?
4. How many numbers are
   there between 1 and 10 ?
5. What is the number
   between 66 and 68 ?
6. Which is near to 8,
   1 or 10 ?
7. Is the number 48 near 50 ?
   or is it near 41 ?
8. Write the numbers
   97, 27, 77, 87, 67, 37, 47, 57
   in the ascending order.
9. Write the two digit
   numbers with 2 at the end.
10. Write the two digit
    numbers with 8 at the beginning.

For answers see at the
bottom of the page.

For study of numbers 100
and above, you may go to
Three Digit Numbers.

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Answers to Exercise
On Two digit Numbers

1. 78, Seventy Eight
2. 60, Sixty
3. 84, Eighty Four
4. 9, nine
5. 67, Sixty Seven
6. 10, ten
7. near 50. near Fifty.
8. 27, 37, 47, 57, 67, 77, 87, 97.
9. 12, 22, 32, 42, 52, 62, 72, 82, 92
10. 80, 81, 82, 83, 84, 85, 86, 87, 88, 89