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Whole Numbers www.mathsrevision.com National 4 NUM 1.2 Rounding to nearest 10,100,1000 Estimating Answers Multiplying & Dividing by 10,100,1000 Multiplying & Dividing by 20, 300 etc.. 18-Jul-15 Created by Mr. Lafferty Maths Dept. Starter Questions www.mathsrevision.com National 4 NUM 1.2 1. 39 x 2 2. Calculate 50% of 750 3. What is the name of the shape will this net make. 4. Calculate the value of the missing angle. 18-Jul-15 Created by Mr. Lafferty Maths Dept. Whole Numbers Rounding to nearest 10, 100 and 1000 www.mathsrevision.com National 4 NUM 1.2 Learning Intention 1. To round numbers to the nearest 10, 100 and 1000. Success Criteria 1. Understand the rules for rounding to the nearest 10, 100, 1000. 2. Apply rules to problems. 18-Jul-15 Created by Mr. Lafferty Maths Dept. Whole Numbers Rounding to nearest 10, 100 and 1000 www.mathsrevision.com National 4 NUM 1.2 To round to the nearest 10 : look at the units digit: - If it is a 0, 1, 2, 3, 4 leave the 10’s digit as it is. - If it is a 5, 6, 7, 8, 9 round the 10’s digit up by 1. To round to the nearest 100 : look at the tens digit: - If it is a 0, 1, 2, 3, 4 leave the 100’s digit as it is. - If it is a 5, 6, 7, 8, 9 round the 100’s digit up by 1. 18-Jul-15 Created by Mr. Lafferty Maths Dept. Whole Numbers Rounding to nearest 10, 100 and 1000 National 4 NUM 1.2 www.mathsrevision.com To round to the nearest 1000 : look at the hundreds digit: - If it is a 0, 1, 2, 3, 4 leave the 1000’s digit as it is. - If it is a 5, 6, 7, 8, 9 round the 1000’s digit up by 1. Example : Round 3467 to the nearest 10, 100, 1000 The nearest 10 : 3467 The nearest 100 : 3467 - look at The nearest 1000 :3467 - look at 18-Jul-15 3470 3500 the tens digit : the hundreds digit:3000 - look at the units digit : Created by Mr. Lafferty Maths Dept. Whole Numbers Rounding to nearest 10, 100 and 1000 National 4 NUM 1.2 www.mathsrevision.com Example : Round 18 565 to the nearest 10, 100, 1000 The nearest 10 : 18 565 - look at the units digit :18 570 The nearest 100 : 18 565 - look at the tens digit : 18 600 The nearest 1000 :18565 - look at the hundreds digit:19 000 18-Jul-15 Created by Mr. Lafferty Maths Dept. Whole Numbers Rounding to nearest 10, 100 and 1000 www.mathsrevision.com National 4 NUM 1.2 Now try Ex 1 & 2 Last 2 columns Ch1 (page 9) 18-Jul-15 Created by Mr. Lafferty Maths Dept. Starter Questions www.mathsrevision.com National 4 NUM 1.2 1. 67 x 7 2. Calculate 20% of 400 3. What is the name of the shape will this net make. 4. Calculate the value of the missing angle. 18-Jul-15 Created by Mr. Lafferty Maths Dept. 42o Whole Numbers Using Rounding to Estimate Answers www.mathsrevision.com National 4 NUM 1.2 Learning Intention 1. To explain how estimate answer by rounding a number to an easier number for mental calculation 18-Jul-15 Success Criteria 1. Be able to round numbers to a whole number. 2. Estimate the answer to a difficult calculation using easier whole numbers. Created by Mr. Lafferty Maths Dept. Whole Numbers Using Rounding to Estimate Answers www.mathsrevision.com National 4 NUM 1.2 It is very important when solving problems that we have a rough idea of the answer we are expecting. Example : Mentally estimate the answer to 42 x 49 Easiest way, is to round the two numbers first 40 x 50 = 400 x 5 = 2000 18-Jul-15 Created by Mr. Lafferty Maths Dept. Whole Numbers Using Rounding to Estimate Answers National 4 NUM 1.2 www.mathsrevision.com Example : Mentally estimate the answer to 104 x 19 Easiest way, is to round the two numbers first 100 x 20 = 1000 x 2 = 2000 Example : Mentally estimate the answer to 878 ÷ 27 Easiest way, is to round the two numbers first 900 ÷ 30 = 90 ÷ 3 = 30 18-Jul-15 Created by Mr. Lafferty Maths Dept. Whole Numbers Using Rounding to Estimate Answers www.mathsrevision.com National 4 NUM 1.2 Now try Ex 3 Ch1 (page 10) 18-Jul-15 Created by Mr. Lafferty Maths Dept. Starter Questions www.mathsrevision.com National 4 NUM 1.2 1. 35.6 + 45.5 2. Calculate 25% of 1000 3. What is the name of the shape will this net make. 4. Calculate the value of the missing angle. 18-Jul-15 Created by Mr. Lafferty Maths Dept. 34o Whole Numbers Multiply by 10, 100, 1000 www.mathsrevision.com National 4 NUM 1.2 Learning Intention 1. 18-Jul-15 To understand how to multiply and divide simple whole numbers by 10, 100, 1000. Success Criteria 1. Understand the simple rules to multiply and divide simple whole numbers. 2. Be able do simple calculations. Created by Mr. Lafferty Maths Dept. Whole Numbers Multiply by 10, 100, 1000 National 4 NUM 1.2 www.mathsrevision.com For this section you need to know your tables To multiply by 10, 100, 1000 To multiply by 10 simply add a zero to the number To multiply by 100 simply add 2 zero’s to the number To multiply by 1000 simply add 3 zero’s to the number Example : Multiply 36 by 10, 100, 1000. Guess 36 rule x 10 = 360 for 1000 18-Jul-15 36 x 100 = 3600 Created by Mr. Lafferty Maths Dept. 36 x 1000 = 36000 Whole Numbers Multiply by 10, 100, 1000 www.mathsrevision.com National 4 NUM 1.2 Example : A box of crisps contain 48 packets. How many in 100 boxes ? 48 x 100 = 4800 18-Jul-15 Created by Mr. Lafferty Maths Dept. Whole Numbers Divide by 10, 100, 1000 National 4 NUM 1.2 www.mathsrevision.com Try and To Divide by 10, 100, 1000 write down rule forTo divide by 10 remove a zero from the number 100, 1000 To divide by 100 remove 2 zero’s from the number To divide by 1000 remove 3 zero’s from the number Example : Divide 54000 by 10, 100, 1000. 54000÷ 10 = 5400 54000 ÷ 100 = 540 54000 ÷ 1000 = 54 18-Jul-15 Created by Mr. Lafferty Maths Dept. Whole Numbers Divide by 10, 100, 1000 www.mathsrevision.com National 4 NUM 1.2 Example : A box contains 1000 cups. How many boxes are needed to hold 7000 ? 7000 ÷ 1000 = 7 18-Jul-15 Created by Mr. Lafferty Maths Dept. Whole Numbers Multiply & Divide by 10, 100, 1000 www.mathsrevision.com National 4 NUM 1.2 Now try Exercise 4 & 5 Ch1 (page 11) 18-Jul-15 Created by Mr. Lafferty Maths Dept. Starter Questions www.mathsrevision.com National 4 NUM 1.2 1. 76 - 54 2. Calculate 75% of 400 3. What is the name of the shape will this net make. 4. Calculate the value of the missing angle. 18-Jul-15 Created by Mr. Lafferty Maths Dept. 36o Whole Numbers Multiply or Divide by 20,300,4000 www.mathsrevision.com National 4 NUM 1.2 Learning Intention 1. To explain how to divide by 20, 300, 4000 etc using our knowledge so far. Success Criteria 1. Understand the two step process to multiply or divide by 20, 300 etc… 2. Show all working. 18-Jul-15 Created by Mr. Lafferty Maths Dept. Whole Numbers Multiply or Divide by 20,300,4000 www.mathsrevision.com National 4 NUM 1.2 By combining our knowledge so far of “multiplying / dividing by 10, 100, 1000” and “multiplying / dividing by a single digit” we can do harder calculations. We use a TWO step process. Example 1 : Calculate 20 x 52 20 can be written as 2 x 10 so we have : 2 x 10 x 52 = Step 1 : 10 x 52 = 520 18-Jul-15 Step 2 : 2 x 520 = 1040 Created by Mr. Lafferty Maths Dept. Whole Numbers Multiply or Divide by 20,300,4000 National 4 NUM 1.2 www.mathsrevision.com Example 2 : Calculate 44 x 30 30 can be written as 10 x 3 so we have : 44 x 10 x 3 = Step 1 : 44 x 10 = 440 Step 2 : 440 x 3 = 1320 Example 3 : Calculate 300 x 35 300 can be written as 3 x 100 so we have : 3 x 100 x 35 = Step 1 : 100 x35 = 3500 18-Jul-15 Step 2 : 3500 x 3 =10500 Created by Mr. Lafferty Maths Dept. Whole Numbers Multiply or Divide by 20,300,4000 www.mathsrevision.com National 4 NUM 1.2 Example 4 : Calculate 16000 ÷ 200 Since 200 divide by 100 then divide by 2: 16000 ÷ 100 ÷ 2 = Step 1 : 16000 ÷ 100 = 160 Step 2 : 160 ÷ 2 = 80 18-Jul-15 Created by Mr. Lafferty Maths Dept. Whole Numbers Multiply or Divide by 20,300,4000 www.mathsrevision.com National 4 NUM 1.2 Example 5 : Calculate 120000 ÷ 6000 Since 6000 divide by 1000 then divide by 6: 120000 ÷ 1000 ÷ 6 = Step 1 : 120000 ÷ 1000 = 120 Step 2 : 120 ÷ 6 = 20 18-Jul-15 Created by Mr. Lafferty Maths Dept. Whole Numbers Multiply or Divide by 20,300,4000 www.mathsrevision.com National 4 NUM 1.2 Now try Ex 6 & 7 Ch1 (page 12) 18-Jul-15 Created by Mr. Lafferty Maths Dept.