FS Maths Level 2- March 08, 2023 (Decimals).

1. FUNCTIONAL
SKILLS MATH

2. Starter: Begin with
decimals
Addition, subtraction,
multiplication, division
Comparing decimals,
rounding and estimating
Extension activity, if time:
worksheets
Today!

3. Decimals
A decimal is any number with a decimal point. Decimals are numbers
that lie between whole numbers, e.g. 90.2, 4.57 or 39.41285

4. Decimal Place Value
The digits after the decimal point also have values. The value
decreases the further right you move away from the decimal point.
e.g. the number 39.4128539 can be split up into:

5. Adding Decimals
Adding decimals without a calculator uses the same column method as for
whole numbers, you just have to make sure to line up the decimal points.
Example: Calculate 6.436 + 8.992
Use the column method for addition, like below:
Therefore,
6.436 + 8.992 = 15.428

6. Subtracting Decimals
Subtracting decimals without a calculator uses the same column method as
for whole numbers, you just have to make sure to line up the decimal points and
add 00’s to the end of a number (if necessary) so that both numbers have the
same number of decimal places.
Example: Calculate 567.63 - 92.478
Use the column method for subtraction like below, adding a 0 so that both
numbers have 3 decimal places:
Therefore,
567.63 - 92.478 = 475.152

7. Try solving the following practice problems to get a
thorough understanding of the addition and subtraction
of decimal numbers.
1. Add the decimals: 84.956 and 210.28163
2. Add 3.25, 0.075 and 5
3. Subtract 54.12 from 64.
4. Subtract 72.3261 from 80

8. Multiplying Decimals
To multiply decimals without a calculator, use the following steps:
Step 1: Convert the decimals to whole numbers by moving the decimal point
to the right.
Step 2: Take note of how many decimal places that were moved in total.
Step 3: Complete the column method or grid method for multiplying without
a calculator.
Step 4: Move the same number of decimal places back at the end. Now you
have the final answer.
Example: Calculate 7.68 times 2.5 (7.68×2.5)
The decimal point is moved one time on 2.5 to make it 25 and two times
on 7.68 to make it 768. So, 3 decimal places were moved altogether.
Now, use the column method as seen (or the grid method):
Finally, move the decimal point back the same number of times
as before. So, move it 3 times to the left.
The final answer is therefore:
7.68 x 2.5 = 19.200 =19.2

9. Find the product.
1. 0.4 × 0.7
2. 2.45 × 0.09
3. 8.3 × 10.9
4. 10.8 × 0.08
5. 2.546 × 1.5

10. Dividing Decimals
To divide decimals without a calculator, use the following steps:
Step 1: Write the division as a fraction.
Step 2: Multiply the top and bottom by 10 until the bottom is no longer a
decimal.
Step 3: Complete the bus stop method for dividing numbers without a
calculator.
Step 4: This gives the final answer.
Example: Calculate 9.184÷1.4
Write the division as a fraction:
9.184÷1.4 as a fraction = 9.184 /1.4
Multiply the top and bottom by 10 until the bottom is no longer a decimal:
9.184 x 10 = 91.84
1.4 x 10 = 14
91.84 / 14
Use the bus stop method to calculate the division:
9.184÷1.4=6.56

11. Find the quotient and (if) remainder
1.0.55 ÷ 0.05
2.0.66 ÷ 0.03
3.0.46 ÷ 0.02
4.20.35 ÷ 0.005
5.15. 0.83 ÷ 0.415

12. Comparing Decimals
You can compare and order decimals, just like you can order numbers. However,
ordering decimals is a little harder.
To order decimals, you need to look at each number in turn and compare them
starting with the first digit.
Example: Put the following numbers in order from smallest to largest.
1.101, 0.11, 1.10, 0.01

13. Step 3: Then, look at the other numbers that
were previously crossed out, and compare
these.
1.101, 1.10
Look at the second digit for each number and
compare them, but these are the same. So,
compare the third digit, but these again are the
same.
The first number has a fourth digit, but the
second number does not, so eliminate the first
number since it is bigger.
So, 1.10 is the third smallest and 1.101 is the
biggest.
Step 4: Finally, write down the correct order:
0.01, 0.11, 1.10,1.101
Step 1: Look at the first digit of each number
and compare them.
1.101, 1.10
0.11, 0.01
2 numbers start with 1 and 2 numbers start
with 0. Since we want the smallest first, we can
eliminate the 2 largest.
Step 2: Now, look at the second digits of each of
the remaining numbers and compare them.
0.11, 0.01
The second digit for the first number is a 1 and
for the second number it is a 0, so the first
number it is bigger, so we can eliminate this.
So, the smallest number is 0.01 and 0.11 is the
second smallest.
Example: Put the following numbers in order from smallest to largest.
1.101, 0.11, 1.10, 0.01

14. QUESTIONS
Calculate 81.07 + 31.862 without using a calculator.
Calculate 18.63 ÷ 2.3 without using a calculator.
Calculate 3.566 × 14 without using a calculator.
Aimee buys 60 boxes of pencils for her school. Each box contains 40 pencils, with
each pencil costing 15p.
How much does she spend on pencils altogether?
Calculate:
a) 5.7×100
b) 42×10
c) 13.1×1000
Which number is bigger, 5.0461 or 5.0470?

15. ROUND AND ESTIMATE DECIMALS

16. Estimating is an important part of mathematics and a very handy tool for everyday life. Get in the
habit of estimating amounts of money, lengths of time, distances, and many other physical
quantities.
Rounding off is a kind of estimating.
To round off decimals:
1.Find the place value you want (the "rounding digit") and look at the digit just to the right of it.
2.If that digit is less than 5, do not change the rounding digit but drop all digits to the right of it.
3.If that digit is greater than or equal to five, add one to the rounding digit and drop all digits to the
right of it

17. Problem Hakim wrote checks for $64.20, $47.89, and $95.80. Estimate the
total of all three checks.
To estimate the total, first round each
of the check values. You want to round
to the nearest $10 in this example.
64.20 → 60
47.89 → 50
95.80 → 100
Since 4 < 5, round to 60.
Since 7 > 5, round up to 50.
Since 5 = 5, round up to 100.
60 + 50 + 100 = 210 Add the estimates to find the estimated
total.
Answer The total estimate for the three checks is $210.

18. Example
Problem Sherry has $50 and wants to buy CDs that cost $11.50
each. About how many CDs can she buy?
Round $11.50 to the nearest
whole number.
11.50 → 12.00 Since you want to make sure
that Sherry has enough money,
round up to 12.00 or 12.
50 ÷ 12 = 4 R2 Divide. The amount of the
remainder is not important.
Answer Sherry can buy about 4 CDs with $50.

20. https://www.mathplayground.com/number_conundru
m/number_conundrum_decimal_numbers.html
https://mrnussbaum.com/lunch-lady-online-game
ACTIVITY TIME!

21. Practice Worksheets