1. Decimals & 4 Operations Primary 4 Mathematics

2. Decimals & 4 Operations 2 Chapter Learning Outcomes  Addition with decimals  Subtraction with decimals  Multiplication with decimals  Division with decimals  Estimation of decimals

3. Decimals & 4 Operations Addition with Decimals Mrs Koh bought 0.5 kg of grapes and 1.6 kg of oranges. What was the total mass of fruits she bought altogether? 3 Ones. Tenths. ●●●●● ●. ● 2. 1 I can show this using a place value chart.

4. Decimals & 4 Operations Addition with Decimals 4 Mrs Koh bought 0.5 kg of grapes and 1.6 kg of oranges. What was the total mass of fruits she bought altogether? I can also use vertical addition to solve this. Always add from right to left. She bought 2.1 kg of fruits altogether.

5. Decimals & 4 Operations Addition with Decimals Andy had $5.95 in his pocket. His father gave him another $3.55. How much does Andy have altogether now? 5 Ones. TenthsHundredths ●●●●●. ●●●● ●●●●● ●●●. ●●●●● 9. 50 Using a place value chart:

6. Decimals & 4 Operations Addition with Decimals 6 Andy had $5.95 in his pocket. His father gave him another $3.55. How much does Andy have altogether now? Using vertical addition: He has $9.50 altogether now.

7. Decimals & 4 Operations Subtraction with Decimals Jansen had 1.3 litres of fruit juice. He drank 0.5 litres during lunch. How many litres of fruit juice does he have left? 7 Ones. Tenths ●. ●●●. ●●●●● ●●● 0. 8 I can show this using a place value chart.

8. Decimals & 4 Operations Subtraction with Decimals Jansen had 1.3 litres of fruit juice. He drank 0.5 litres during lunch. How many litres of fruit juice does he have left? 8 I can also use vertical subtraction to solve this. He has 0.8 litres left.

9. Decimals & 4 Operations Subtraction with Decimals Suriani had 3.05 m of ribbon. She used up 0.76 m of it. What is the length of ribbon that she has left? 9 Ones. TenthsHundredths ●●●. ●●●●● ●●. ● ●●●● ●●●●● 2. 29 Using a place value chart:

10. Decimals & 4 Operations Subtraction with Decimals Suriani had 3.05 m of ribbon. She used up 0.76 m of it. What is the length of ribbon that she has left? 10 Using vertical subtraction: She had 2.29 m of ribbon left.

11. Decimals & 4 Operations Multiplication with Decimals 11 Angie poured 4 cartons of milk, each with 2.4 litres, into a mixing bowl. How many litres of milk were there altogether? I can show this using a place value chart. Ones. Tenths ●●. ●●●● ●●. ●●●● ●●. ●●●● ●●. ●●●● 9. 6 4 x 2.4

12. Decimals & 4 Operations Multiplication with Decimals 12 Angie poured 4 cartons of milk, each with 2.4 litres, into a mixing bowl. How many litres of milk were there altogether? I can also use vertical multiplication to solve this. There were 9.6 litres of milk altogether.

13. Decimals & 4 Operations Multiplication with Decimals 13 Dinesh ate 3 cookies, each with mass 1.45 g. What was the total mass of the cookies that he ate? Using a place value chart: Ones. TenthsHundredths ●. ●●●●●●●●● ●. ●●●●●●●●● ●. ●●●●●●●●● 4. 35 3 x 1.45

14. Decimals & 4 Operations Multiplication with Decimals 14 Dinesh ate 3 cookies, each with mass 1.45 g. What was the total mass of the cookies that he ate? Using vertical multiplication: He ate 4.35 g of cookies.

15. Decimals & 4 Operations Division with Decimals 15 Jagdeep had a strip of paper measuring 1.8 m. He cut it into 4 equal strips. How long is each shorter strip of paper? I can show this using a place value chart. Ones. TenthsHundredths ●. ●●●●. ●●●●● 0. 45

16. Decimals & 4 Operations Division with Decimals 16 Jagdeep had a strip of paper measuring 1.8 m. He cut it into 4 equal strips. How long is each shorter strip of paper? I can show this using long division. Each strip of paper is 0.45 m long.

17. Decimals & 4 Operations Division with Decimals 17 Zhiwei wants to divide 19 litres of water equally into 6 pots. Find the volume of water in each pot, correct to 2 decimal places. Divide to 3 decimal places, then round off the answer to 2 decimal places. 3.166.. ≈ 3.17 There are about 3.17 litres of water in each pot.

18. Decimals & 4 Operations Estimation of Decimals 18 To round off to the nearest whole number, look at the digit in the tenths place. I can round off the decimal that I obtain to check whether it is a reasonable answer. Addition, Subtraction, Multiplication Division If the tenths digit is 1, 2, 3, or 4, round down to the smaller ones digit If the tenths digit is 1, 2, 3, or 4, round down to the smaller whole number that is divisible If the tenths digit is 5, 6, 7, 8 or 9, round up to the greater ones digit If the tenths digit is 5, 6, 7, 8 or 9, round up to the greater whole number that is divisible

19. Decimals & 4 Operations Estimation of Decimals Find the sum of 13.8 and 6.3, then check your answer using estimation. 19 Calculation: 13.8 + 6.3 = 20.1 Estimation: 13.8 ≈ 14 and 6.3 ≈ 6 14 + 6 = 20 20.1 ≈ 20 My answer is reasonable.

20. Decimals & 4 Operations Estimation of Decimals Find the value of 35.72 – 23.15, then check your answer using estimation. 20 Calculation: 35.72 – 23.15 = 12.57 Estimation: 35.72 ≈ 36 and 23.15 ≈ 23 36 – 23 = 13 12.57 ≈ 13 My answer is reasonable.

21. Decimals & 4 Operations Estimation of Decimals Find the value of 50.04 ÷ 6, then check your answer using estimation. 21 Calculation: 50.04 ÷ 6 = 8.34 Estimation: 50.04 ≈ 48 48 ÷ 6 = 8 8.34 ≈ 8 My answer is reasonable. 50.04 ÷ 6 48 ÷ 6 54 ÷ 6

22. Decimals & 4 Operations Example Solve the following. Estimate to check your answers. 22 (a) 13.402 + 5.05 = _______ (b) 62 – 3.288 = _______ (c) $24.05 – $4.89 = _______ (d) 7.16 g x 9 = _______ (e) 5.75 km ÷ 5 = _______ 18.452 58.712 $19.16 64.44 g 1.15 km

23. Decimals & 4 Operations 23 Reference - Textbooks Learning Outcomes Addition with decimals 4B Pg 48 – 51, 58 – 60 4B Pg 32 – 37, 57 – 62 Subtraction with decimals 4B Pg 52 – 57, 58 – 60 4B Pg 38 – 42, 57 – 62 Multiplication with decimals 4B Pg 61 – 65, 77 – 80 4B Pg 43 – 48, 57 – 62 Division with decimals 4B Pg 66 – 72, 77 – 80 4B Pg 49 – 56, 57 – 62 Estimation of decimals 4B Pg 73 – 76, 77 – 80 4B Pg 32 – 63