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Vol. 10 No. 2 SY 2004-2005 ISSN 0118-2595 Jenny’s Homework Bird’s Nests Subtracting Across Zero Articles • Price Chart 3 e-Pages JENNY’S HOMEWORK By Dr. Alice C. Raganas W hile on their way home from school, Jenny was telling her parents about their lesson in Math. “My teacher taught us the Roman numerals and their corresponding Hindu-Arabic numbers. The ancient Romans used the letters I, V, X, L, C, D, and M to form numerals. These Roman numerals have a value of 1, 5, 10, 50, 100, 500, and 1 000, respectively. She also taught us how to read Roman numerals. We read Roman numerals from left to right. She also mentioned some rules we must follow when we use Roman numerals. For our assignment, she asked us to list down the places where we usually see the Roman numerals,” explained Jenny. Her father slowly stopped the car. “Look at that building. What can you see?” Mr. Dalen pointed to the top of the building. “It says MDCCLIX, and it means 1759, Dad. What does it mean?” “It means that this building was built in the year 1759,” her father replied. “By the way, I have here with me a book. Look at the chapter page. How does the number of each chapter written in this book?” asked Mrs. Dalen. “It says Chapter XXVI, meaning Chapter 26,” replied Jenny. “How about the book copyright date? How was it written?” her father asked. “The book says, MCMLXXXIV meaning 1984,” replied Jenny. At home, father got a CD. “Come, Jenny, let’s watch this CD,” Mr. Dalen invited Jenny, showing the CD to her. MATH Talino Grade 3 Vol. 10 No. 2 e-Pages 2 After a few minutes, Mr. Dalen paused the movie. “The movie copyright date was MCMXCV, which means that this movie was copyrighted in the year 1995,” he explained brieﬂy. “Dad, do you mean we also use Roman numbers in this movie?” the daughter asked. “Yes, you are right. You know that the main character of the movie was King Richard III. We also use Roman numerals in writing names of persons,” her father added. “Now, I have answers to our homework. Roman numbers are used in writing the following: 1. Chapter number of a book 2. Book copyright date 3. Name of a person 4. Date on building 5. Movie copyright date “Thanks, Dad,” said Jenny. “You’re welcome, Jenny.” Try This Write each of the following as a standard numeral. 1. Chapter of a book XVI __________ 2. Book copyright date MCMXCVIII __________ 3. King Philip II __________ 4. Date on Building MCMLXXXIX __________ 5. Movie copyright date MMIV __________ MATH Talino Grade 3 Vol. 10 No. 2 e-Pages 3 BIRD’S NESTS By Dr. Alice C. Raganas L ilibeth and Sarah lived in the province. Last summer, the two friends volunteered to help a scientist keep track of bird’s nests. They had been doing this for two years already. As volunteers, they were always on the lookout for bird’s nests. As early as dawn until sunset, they would start searching for nests. Every day, they would wake up early to do their chores. Lilibeth prepared breakfast, while Sarah prepared the materials needed for their hike to the mountains and forests. One day, after having their lunch, Sarah told Lilibeth that she found 4 380 nests last year. “I found 6 645 nests last year,” said Lilibeth. “What if we will combine the number of nests we found in one year, how many nests have we found all together?” asked Lilibeth. The two friends made a computation: Sarah’s way 4 380 + 6 645 11 025 MATH Talino Grade 3 Vol. 10 No. 2 e-Pages 4 Lilibeth’s way First 1 estimated. 4 000 + 7 000 = 11 000 Then I used a calculator. 4 380 + 6 645 = 11 025 11 025 is close to 11 000 So, we have found 11 025 bird’s nests. “Why did you estimate before you used the calculator?” asked Sarah. “I estimated ﬁrst to decide if the sum of 4 380 and 6 645 is more or less than 11 000,” replied Lilibeth. Try This 1. Find the sum of 937 and 4 619. 2. Estimate to decide if the sum of 9 637 + 2 935 is greater than or less than 13 000. 3. Who found the most bird’s nests — Sarah or Lilibeth? Explain how did you know. 4. How much more bird’s nests did Lilibeth ﬁnd than Sarah? 5. Both women search for nests between 8 to 12 hours a day. If Lilibeth begins searching at 8:15 a.m., what time will it be 10 hours later? MATH Talino Grade 3 Vol. 10 No. 2 e-Pages 5 SUBTRACTING ACROSS ZERO By Dr. Alice C. Raganas I n her Math class, Ms. Gonzales tells two students to ﬁnd the difference between 206 and 129. Alvin and Pamela stand up to solve the equation on the blackboard. After a few more minutes, the two students have ﬁnished the task almost at the same time. “Look at Alvin’s work and at Pamela’s work. Do you have any comment?” Ms. Gonzales asks the class. The pupils are silent. Everybody’s attention is on the solutions that Alvin and Pamela did. Alvin’s way Pamela’s way 9 1 10 16 1 9 16 206 –129 77 206 –129 77 After awhile, Ms. Gonzales calls up Alvin and Pamela to explain how each of them got their answer. Alvin explains his answer ﬁrst. “Since there are no tens, I’ll regroup the hundreds. Then, I can regroup the tens. Now, I can subtract the ones,” Alvin explains conﬁdently. MATH Talino Grade 3 Vol. 10 No. 2 e-Pages 6 “Two hundreds is 20 tens,” Pamela said. “One less ten is 10 more ones. I’ll add to check. 77 + 129 = 206. The answer is correct,” Pamela explains her answer. Try This A. Subtract. Check each answer. 1. 405 – 91 2. 605 – 496 3. 700 – 33 4. 405 – 257 5. 406 – 138 6. 905 – 296 7. 603 – 357 8. 704 – 635 9. 610 – 238 10. 307 – 89 B. Answer the following questions. 1. What is 602 minus 316? 2. What is the difference between 300 and 158? 3. What number could you subtract from 301 without regrouping. What is the difference? 4. Ms. Uy bought a new lampshade for P 789. She paid for it with a P1 000.00. How much change did she get? 5. Some students need to wash 100 cars to raise money for a school trip. They have washed 56 cars. About how many more cars do they need to wash? MATH Talino Grade 3 Vol. 10 No. 2 e-Pages 7 Answers to “Try This” Jenny’s Homework 1. 2. 3. 4. 5. 16 1998 2 1989 2004 Bird’s Nests 1. 2. 3. 4. 5. 5556 10 000 + 3 000 = 13 000 Lilibeth 6645 > 4380 2265 bird’s nests 6:15 p.m. Subtracting Across Zero A. 1. 314 2. 109 3. 667 4. 148 5. 268 6. 609 7. 246 8. 69 9. 372 10. 218 B. 1. 2. 3. 4. 5. 286 142 300, 1 P211.00 44 cars MATH Talino Grade 3 Vol. 10 No. 2 e-Pages 8