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Tuesday, September 21. Agenda. Bell Work. Fill in planner Practice 4-1 Enrichment 4-1 (E.C.) Bell Work Go over Ch. 1 Test Notetaking WS (Divisibility and Factors) Group Work. Objective: Students will be able to identify factors and use divisibility rules.
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Tuesday, September 21 Agenda Bell Work • Fill in planner • Practice 4-1 • Enrichment 4-1 (E.C.) • Bell Work • Go over Ch. 1 Test • Notetaking WS (Divisibility and Factors) • Group Work
Objective: Students will be able to identify factors and use divisibility rules
“Divisible by” means: If you divide one number by another, the result is a whole number WITHOUT a remainder. Examples: 12 ÷ 6 = 2 No remainder 15 ÷ 5 = 3 No remainder
Divisibility Rule 2 A number is divisible by 2 if it ends in 0, 2, 4, 6, or 8. Examples: 78 3470
Now You Try: Which number IS NOT divisible by 2? 572 1464 249 Need More Practice: Numbers Divisible by 2
Divisibility Rule 5 A number is divisible by 5 if it ends in 0 or 5. Examples: 615 ends in a 5 1480 ends on a 0
Now You Try: Which number IS NOT divisible by 5? 9820 779 560 Need More Practice: Numbers Divisible by 5
Divisibility Rule 10 A number is divisible by 10 if it ends in 0 Examples: 1320 1320 ÷ 10 = 132 100 100 ÷ 10 =10
Now You Try: Which number IS NOT divisible by 10? 560 4101 180
numbers end in 1, 3, 5, 7, or 9 and are not divisible by 2 Odd
Divisibility Rule 3 A number is divisible by three if the sum of the digits is divisible by 3. Examples: 75 7 + 5 = 12 12 ÷ 3 = 4 No Remainder 369 3 +6 + 9 = 18 18 ÷ 3 = 6 No Remainder
Now You Try: Which number IS NOT divisible by 3? 572 1464 279 Need More Practice: Numbers Divisible by 3
Divisibility Rule 9 A number is divisible by 9 if the sum of the digits is divisible by 9. Examples: 963 9 + 6 + 3 = 18 18 ÷ 9 = 2 5445 5 + 4 + 4 + 5 =18 18 ÷ 9 =2
Now You Try: Find the number that IS NOT divisible by 9. 9873 630 5541 Need More Practice: Numbers Divisible by 9
Factors One integer is a factor of another integer if it divides that integer with a remainder of zero. Ex. factors of 20 1, 20 2, 10 4,5 The factors of 20 are 1, 2, 4, 5, 10, 20
Examples1) Divisibility by 2, 5, and 10 • 1028 by 2 ; 1028 ends in • 572 by 5 ; 572 doesn’t end in or c) 275 by 10 ; 275 doesn’t end in 8 yes no 5 0 no 0
Examples2) Divisibility by 3 and 9 • 1028 by 3 1+0+2+8=11; 11 is not divisible by • 522 by 9 ; 5+2+2=9; 9 is divisible by no 3 yes 9
Examples3) Using Factors Find pairs of factors of 35 1 x 35 5 x 7 There can be 5 rows of students or 7 rows of students. 7 5
Quick Check • Yes; the last digit is 0 • No; the last digit is not 0 • No; the last digit is not 0, 2, 4, 6, or 8 • Yes; the last digit is 2 • No; the sum of the digits is not divisible by 9 • No; the sum of the digits is not divisible by 3 • Yes; the sum of the digits is divisible by 3 • Yes; the sum of the digits is divisible by 9
Quick Check (2) • 1, 2, 5, 10 • 1, 3, 7, 21 • 1, 2, 3, 4, 6, 8, 12, 24 • 1, 31
Quick Check (3) • There could be 6 rows of 6 students, 4 rows of 9 students or 9 rows of 4 students.
Objective: Students will be able to identify factors and use divisibility rules
Definition • Prime Number – a number that has only two factors, itself and 1. 7 7 is prime because the only numbers that will divide into it evenly are 1 and 7.
Examples of Prime Numbers 2, 3, 5, 7, 11, 13, 17, 19 Special Note: One is not a prime number.
Definition • Composite number – a number that has more than two factors. 8 The factors of 8 are 1, 2, 4, 8
Examples of Composite Numbers 4, 6, 8, 9, 10, 12, 14, 15 Special Note: Every whole number from 2 on is either composite or prime.
Our Lonely 1 It is not prime because it does not have exactly two different factors. It is not composite because it does not have more than 2 factors. Special Note: One is not a prime nor a composite number.