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We can write and understand decimal numbers to two places
Year 4 Unit 15a
What we are learning:
- The numbers we use in everyday life are decimal numbers. “Decimal number” can also be used as a way of describing a number that includes a decimal point i.e. 1.9 or 2.78
- The columns after the decimal point have specific meaning (just like the columns before the decimal point).
Thousands, Hundreds, Tens, Units, decimal point, tenths, hundredths
- It can be confusing that a tenth is bigger than a hundredth but the same rule that we already know applies – every time we move one column to the right the value gets ten times smaller. Every time we move one column to the left the value gets ten times bigger.
- Similar words where only the ending is different (ten / tenth) can cause confusion also.
- One and one tenth is written as 1.1 the 1 before the decimal point denotes 1 unit, the 1 after the decimal point denotes 1 tenth.
- Children regularly miswrite money amounts using decimal notation. The most common example is “three pounds and seven pence” written as £3.7 which actually denotes three pounds and seventy pence as the seven is in the tenths column.
ACTIVITY 1: WRITING DECIMAL NUMBERS AND ORDERING THEM
ACTIVITY 2: WRITING DECIMALS AS AMOUNTS OF MONEY
Activities you can do at home
Cut out the decimal number cards on sheet “Write on!” and put them into an envelope. Take it in turns to pull out a card and then write the decimal number using digits
Using the decimal numbers written in digits from “Write on!” choose three numbers to position on the number line provided “Decimal number line”.
Discuss the exact placing of the decimal number as the number line does not show hundredths. i.e.
Where shall we place 1.62?
Next to the 1.6
Is it bigger or smaller than 1.6?
How do you know 1.62 is bigger than 1.6?
It has an extra 2 hundredths
Do you think it should go closer to 1.6 or 1.7?
Closer to 1.6
Can you tell me a decimal number that could go near to 1.7? …
Using the decimal numbers written in digits from “Write on!” discuss (with paper to draw on and real coins if possible) what these amounts would be worth if they were money i.e. seven units and nine tenths now written as
What do you think the 7 represents?
Can you draw that for me/ make that out of the coins in front of us?
What do you think the 9 represents?
The 9 is in the tenths column, one tenth of £1 is 10p. Do you still think it
is worth 9p?
No, 9 ten pence coins.
What is the best way to say that?
Can you draw that for me/ make that out of the coins in front of us? …
If your child:
Tries to put the decimal point in a column rather than on the line between the units and tenths
Correct them as this will prevent them from setting calculations out easily later on. It could also confuse the value of digits nearby.