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Everyday Math. 5 th Grade: Unit One . Unit One Vocabulary. Rectangular array: an arrangement of objects in rows and columns. Each row has the same number of objects and each column has the same number of objects.
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Everyday Math 5th Grade: Unit One
Unit One Vocabulary • Rectangular array: an arrangement of objects in rows and columns. Each row has the same number of objects and each column has the same number of objects. • Factors – numbers that you multiply together to get a product • Factor pair – two numbers that you multiply together to get a product. • Product – the answer you get when you multiply factors together • Divisibility - A number is divisible by another number if it goes in evenly (no remainder) • Composite number – a number that has more than 2 factors • Prime number – a number that has exactly 2 factors (1 and itself) • Square number – a number that makes a square array (2x2, 4x4, 5x5, etc.) • Exponential notation - numbers written with exponents • Exponent - a small number written to the right and above the base number to show how many times the base number is multiplied by itself. • Square root – when you “unsquare” a square number. (example: The square root of 36 is 6 (6x6 =36)) • Prime factorization - writing a number as a product of all prime numbers
Divisibility tests • Divisible by 2 • A number is divisible by 2 if the last digit (number in the one’s place ) is even or 0 • (2, 4, 6, 8, 0) • 346 715Χ • Divisible by 5 • A number is divisible by 5 if the last digit is 5 or 0 • 450 735 569Χ • Divisible by 10 • A number is divisible by 10 if the last digit is 0 • 230 455Χ
Divisibility tests continued… • Divisible by 3 • Add up all the digits in the number. If the sum is divisible by 3, so is the whole number. • 246 451 Χ • (2+4+6=12) (4+5+1=10) • 12 is divisible by 3, so is 246 10 is not divisible by 3, neither is 451 • Divisible by 4 • Look at the last two digits of a number. If the number that the two digits form is divisible by 4, so is the whole number. • 2,232 7,311 Χ • 32 is divisible by 4, so is 2,232 11 is not divisible by 4, neither is 7,311
Divisibility tests continued … • Divisible by 6 • A number is divisible by 6 only if it is both divisible by 2 and 3. • 741 Χ • Divisible by both 2 &3 Divisible by 3, but not 2 • Divisible by 9 • Add up all the digits in the number. If the sum is divisible by 9, so is the whole number. • 846 451 Χ • (8+4+6=18) (4+5+1=10) • 18 is divisible by 9, so is 846 10 is not divisible by 9, neither is 451
Prime numbers – numbers that only have two factors (one and itself.) Composite numbers – numbers that have more than 2 factors
Finding all of the factors for a number: Step 1: Always begin with the number one. 1 x 24 = 24 Step 2: move on to the number two. 2 x 12 = 24 Step 3: continue on until you start repeating numbers. (the next number to check after 4 is 5. 5 doesn’t go into 24 and so you move on to 6. 6 has already been used so you know you have found all of your factors.)
Prime Factorization: writing a number as a product of all prime factors • Step 1: Divide number into a any factor pair. • Step 2: Circle any number that can't be broken • down any more (prime). • Step 3: Continue to break down numbers until • you are left with all prime numbers. • Step 4: Connect all prime numbers with • x symbols from least to greatest. 3 x 3 x 5 • If possible, write your answer in exponential notation 3² x 5 • Check: What is 3 x 3 x 5 (or 3² x 5) ?
Sources: • -EverdyayMath Student reference book • -Some examples taken from: Mr.Wrinkle.net/unit1