CHAPTER 1 BEFORE AND AFTER SCENARIOS

Transcription

1 CHAPTER 1 BEFORE AND AFTER SCENARIOS 1.5 CASE 1 CASE 2 :Solution to Problems Involving Case 1 Case 2 :LET S APPLY: Question 1: Case 1: Case 2: Ben Andy Total Ben Andy Total 1 unit 3 units 2 units 2 units Change Change +6-6 After 1 unit 3 units 4 units After Total Unchanged Compare Ben s before-choclolates: 1 unit units 6 1 part x 2= 2 units 1 part x 2= 2 units 2 part x 2= 4 units 1 unit 11 Ben 11+5 = 16 Andy 33-5 = 28 Christoper = 12 ( ) = 56 : There are 56 chocolates in the packet.

2 Question 2: Case 1: Case 2: Jasmine Niece Diff Jasmine Niece Diff 40 parts 20 parts 27 parts 7 parts Change After Change units x 20 = 40 parts Difference Unchanged 1 unit x 20 = 20 parts Compare Jasmine s before age: 40 parts 8 27 parts unit x 20 = 20 parts After 27 parts 7 parts 20 parts 13 parts 13 1 part = 1 Jasmine 40 8 = 32 : Jasmine is 32 years old.

3 Question 3: Case 1: Case 2: Boys Girls Total Boys Girls Total 3 parts 4 parts 6 parts 5 parts Change -10 Change -10 After 1 units x 3 = 3 parts Total Unchanged 2 unit x 3 = 6 parts Compare before-boy: 3 parts parts 2 parts 10 1 part 10 2 = 5 9 parts x = 55 3 units x 3 = 9 parts After 5 parts 4 parts 9 parts There are 55 pupils in the class

4 Question 4: Elaine Fion Elaine Fion 1 unit units 6 units units Change - 20 Change + 80 After 1 unit 2 units After Fion s money is unchanged Compare Elaine s before-money: 1 unit units 80 3 parts x2 = 6 units 1 part x2 = 2 units 5 units unit = 20 1 unit = 40 (Elaine) 2 units 20 x 2 = 40 (Fion) Elaine has $40 and Fion has $40

5 Question 5: Ginny Holly Ginny Holly 1 unit 3 units 3 parts part Change -1 unit -3 units Change -3 parts -1 part After After All Changing Quantities Compare Holly s before-money: 1 parts 3 units 3 parts 3 x3 = 9 units Compare Ginny s before money: 1 unit parts units unit = units 3 x 150 = 450 (Holly) 1 unit = 1500 (Ginny) (a) Ginny received $1500 (b) Holly received $450

6 HIGHER ORDER PROBLEMS: Question 6: A B A B 2 units 1 unit 1 part part Change -2 unit -1 unit Change -1 part -2 part After After All Changing Quantities Compare Tank B s before-volume: 1 unit 2 parts 2 units 2 x2 = 4 parts Compare Tank A s before-volume: 2 units part parts part = parts 200 x 2 = hour 4 litres 72 hours 4 x 72 = 288 litres = litres of water was left in Tank B after 3 days

7 Question 7: Red Green Red Green 3 units 5 units 4 parts 5 parts Change -1 Change -5 After 3 units 5 units After 4 parts 5 parts All Changing Quantities Compare before- red apples: 3 units parts Compare before- green apples: 5 units 5 parts unit 1 part + 1 x 3 3 units 3 parts part 4 4 parts 4 x 4 = 16 5 parts x 4+ 5 = = 9 There are 9 more green than red apples at first

8 Question 8: Red Blue Red Blue 3 units 5 units 5 parts 6 parts Change -10 Change -30 After 3 units 5 units After 5 parts 6 parts All Changing Quantities Compare before-red pens: 3 units parts x 6 18 units parts Compare before blue pens: 5 units 6 parts + 30 x 5 25 units 30 parts units unit = 30 3 units x = 100 (Red) 5 units 5x30=150 (Blue) = 50 There are 50 more blue than red pens at first

9 Question 9: Jason Kelvin Singapore Malaysia Singapore Malaysia 2 units parts+2 Change -1unit part Change 1unit +14-1part -1 After (I) 1 unit units After (I) 1 part 1 part+1 Change -14 Change -1 After (II) 1 units 2 units After (II) 1 part 1 parts Compare after(i) -Singapore stamps: 1 unit part Compare after(i) Malaysia stamps : 1 part units 1 unit 15 1 part 2x15 1 = 29 2 parts +2 2x = 60 Kelvin had 60 Malaysia stamps at first