Counting in tens. Round numbers. Single and double digit numbers

A ten means exactly 10 ones. We can count not stick by stick but by tens:

10,20,30,40,50,60,70,80,90,100

. That is easier when there are many objects. Round numbers end in

0

(for example,

20

50

). They are easy landmarks when you count by tens. One-digit numbers are written with one digit: from

1

9

. Two-digit numbers use two digits: from

10

99

. A two-digit number has place values: tens and ones.

1\ \text{ten} = 10\ \text{ones}

Count by tens:

10,20,30,40,50,60,70,80,90,100

Round numbers end in

0

One-digit:

1\ldots 9

; two-digit:

10\ldots 99

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