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What is a decimal number?
A decimal number is part of a whole number
What is the value of the 9 in 102.9?
9 ones
9 tens
9 tenths
9 hundredths
Which numerals match the number as words: fifty thousand, two hundred point two
5 200.2
50 200.2
52 200.2
500 002
What does it mean to decompose a number?
When we decompose a number, we break it down into separate parts (hundreds, tens, ones)
What does it mean to compose a number?
When we compose a number, we put it together by adding numbers together
Compose this number: 6 + 200 + 0.09 =
206.09
Decompose this number: 89 013.12 =
80 00 + 9 00 + 1 + 3 + 0.1 + 0.02
80 000 + 9 000 + 10 + 3 + 0.1 + 0.02
80 000 + 9 000 + 10 + 3 + 0.1 + 0.2
80 000 + 9 00 + 13 + 0.1 + 0.02
What is regrouping?
Regrouping is when we change the way a number decomposed or broken down
How can we regroup 45?
30 + 5
45 = 15 + 15 +15
40 + 5
45 + 10 = 55
4.3 x 10
43
4.3 x 100
430
15.2 x 1000
15 200
923 ÷ 10 =
92.3
43.2 ÷ 100
0.432
3.9 ÷ 10 =
0.39
When do we round numbers down to the nearest whole number?
If the number the tenths column is 4 or below ( 1, 2, 3) we round down
