MATH MESSAGE Grade 5, Unit 1, Lessons 1 - 4 5TH GRADE MATH Objectives of Lessons 1 – 4 Unit 1: Place Value and Decimal Fractions Math Parent Letter The purpose of this newsletter is to guide parents, guardians, and students as students master the math concepts found in the St. Tammany Public School’s Guaranteed Curriculum aligned with the state mandated Common Core Standards. Fifth grade Unit 1 covers place value and decimal fractions. This newsletter will address concepts found in Unit 1, Lessons 1 – 4, Multiplicative Patterns on the Place Value Chart. Words to know: Decimal Fraction Digit Equation Exponent Factor Hundredths Place Value Product Tenths Thousandths Decimal Fraction – a fractional number with a denominator of 10 or a power of 10 (10, 100, 1000). It can be written with a decimal point. Digit – any one of the ten symbols, 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 used to write numbers. Equation – statement that two mathematical expressions have the same value, indicated by use of the symbol =. Example: 12=4 x 2 + 4. Exponent – tells the number of times the base is used as a factor or how many times a number is to be used in a multiplication sentence. Example: 103 = 10 x 10 x 10. Factor – A number that is multiplied by another number to find a product. Hundredths – one part of 100 equal parts. hundredth’s place – the second digit to the right of the decimal point. Place Value - the numerical value that a digit has by virtue of its position in a number. Product - the answer to a multiplication problem. Tenths – one part of 10 equal parts; tenth’s place – the first digit to the right of the decimal point. Thousandths – one part of 1,000 equal parts; thousand’s place - the third digit to the right of the decimal point. The students will learn to…. Reason concretely and pictorially using place value understanding to relate adjacent base ten units from millions to thousandths. Reason abstractly using place value understanding to relate adjacent base ten units from millions to thousandths. Use exponents to name place value units and explain patterns in the placement of the decimal point. Use exponents to denote powers of 10 with application to metric conversions. LESSONS 1 - 4 Multiplication and Division Patterns on the Place Value Chart Students will use place value charts to explore changes in place value position as they multiply and divide multi-digit whole numbers and decimals by powers of 10. When we multiply a decimal fraction by a power of 10, the product will be larger than the original number. We are shifting to the left on the place value chart. The number of times we shift to the left depends on the power of 10. When multiplying by 10, we shift one place to the left. If multiplying by 100, we shift two places to the left. If multiplying by 1,000, we shift three places to the left. Example: Record the digits of the first factor on the top row of the place value chart. Draw arrows to show how the value of each digit changes when you multiply. Record the product on the second row of the place value chart. a) 3.452 x 10 = 34.52 (34.52 is 10 times greater than 3.452.) When we divide a decimal fraction by a power of 10, the quotient will be smaller than the original number. We are shifting to the right on the place value chart. The number of times we shift to the right depends on the power of 10. When dividing by 10, we shift one place to the right. If dividing by 100, we shift two places to the right. If dividing by 1,000, we shift three places to the right. a) After a lesson on exponents, Tia went home and said to her mom, “I learned that 104 is the same as 40,000.” She has made a mistake in her thinking. Use words, numbers or a place value chart to help Tia correct her mistake. Tia thinks that 104 means to multiply 1 by 4 and then add 4 zeros behind the 4. She is correct in her thinking of adding 4 zeros, but she was not supposed to multiply 1 by 4. 104 means 10 x 10 x 10 x 10. 10 is being multiplied by itself 4 times or 10,000. 345 ÷ 10 = 34.5 Note: This solution uses both words and numbers. Students could have also solved this problem by drawing a place value chart and shifting 10 four places to the left. Exponents: Students will learn a more efficient way to represent place value units, using exponents. Students will see that the number of zeros in the product (answer) is the same as the number of factors of 10 being multiplied. A honey bee’s length measures 1 cm. Express this measurement in meters. a. Explain your thinking using a place value chart. 1 Example: 104 = 10 x 10 x 10 x 10=10,000 (4 factors of 10 – 4 zeros in the product) 103 = 10 x 10 x 10 = 1,000 (3 factors of 10 – 3 zeros in the product) Students will apply their knowledge of exponents to converting metric units. Example: 3 x 102= 3 x 10 x 10 or 300 Convert 3 meters to centimeters. (1 meter = 100 centimeters) 100 is the same as 102. 3 meters = 300 cm 0 ● 0 1 There are 100 centimeters in 1 meter. To convert to meters from centimeters, I have to divide 1 by 100. To show this on a place value chart, I shifted 1 two places to the right. 1 cm = 0.01 meters b. Explain your thinking using an equation that includes an exponent. SAMPLE PROBLEMS AND ANSWERS Alaska has a land area of about 1,700,000 km2. Florida has a land area 1/10 the size of Alaska. What is the land area of Florida? Explain how you found your answer. 1 meter = 100 centimeters. 1/10 is the same as dividing by 10. To find the area of Florida, I divided 1,700,000 by 10 which equals 170,000. I pictured the place value chart in my head. I shifted the 1,700,000 one place to the right. That shifted one of the zeros to the tenths place. So instead of having 5 zeros, the number now has 4 zeros. 1 ÷ 102 1,700,000 ÷ 10 = 170,000. The land area of Florida is 170,000 km2. 100 is the same as 102. = 1 ÷ (10 x 10) = 1 ÷ 100 = 0.01 m Students are showing that they understand that 102 is 10 x 10 or 100. It is acceptable if students don’t show the step, 1 ÷ (10 x 10).
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