MATHEMATICS GRADE 8-9 NEW NAMIBIAN CARRICULLUM REVISED BY MR. RIAMEKEE N. NGEZEMBA TOPIC 1; NUMBERS GRADE 8 &9 LEANERS SHOULD BE ABLE TO; 1.1 WHOLE NUMBERS • list multiples of numbers smaller than 10 • find the factors of a number • determine if any number in the range of 1 – 100 is prime or composite • find prime factors of numbers and express numbers as products of their prime factors in index notation • determine the Lowest Common Multiple (LCM) and Highest Common Factor (HCF) of up to three given whole numbers • determine an answer to another calculation e.g. if 30 × 25 = 750, work out 31 × 25 or work out 32 × 25 • apply multiplication and division facts to multiply and divide decimals e.g. 0.05 × 7 gives 0.35 since 5 × 7 = 35 and 4.2 ÷ 6 gives 0.7 since 42 ÷ 6 = 7 • recognize where to place decimal point for equivalent calculations e.g. 4.37 × 0.3 = (4.37 ×3) ÷ 10 = 1.311 • apply the four basic operations to whole numbers including the application of BODMAS {brackets, of, division and multiplication (from left to right) is done first, and then addition and subtraction (from left to right)} PRIME NUMBERS ο΄Are numbers that has only two factors; 1 and itself {2, 3, 5, 7, 11, 15, ….} • The table shows the Prime Numbers from 0 – 100 ; Prime factors or Prime Factorization • Product of prime factors → Are factors of a number which are also prime numbers Example; Find the prime factors of 20; 20 = 2 x 2 x 5 (therefore the prime factors of 20 is 2 and 5) • Composite Numbers → Are numbers with more than two factors; {4; 6; 8; 9; 10; ……} the numbers that are not shaded in the prime number table on the previous page are composite numbers EXCLUDING 1. Is 1 a Prime number? NO because 1 has only one factor, meaning that 1 can only go into itself and nothing else. Consider the problem; π ππ π × π − π × π + π + π − ππ ÷ π • B – Complete all operations in Brackets (from left to right) π ππ π × π − π × π + π − ππ ÷ π • O – Complete all operations in Of (x) (from left to right) 8 × π − π × π + π − ππ ÷ π • D (÷) M (×) – Complete all operations in Division and/or Multiplication (from left to right) π × π − π × π + π − ππ ÷ π ππ − π × π + π − ππ ÷ π ππ − ππ + π − ππ ÷ π ππ − ππ + π − π • A (+) S (Λ) – Complete all operations in Addition and/or Subtraction (from left to right) ππ − ππ + π − π ππ + π − π ππ − π 17 Lowest Common Multiple (LCM) • the lowest number where the multiples of two or more numbers are the same /common HINT: List the multiples of each number until you meet the first common one. That is the LCM. Example 1 Find the LCM of 6 and 8; Multiples of 6; 6, 12, 18, 24, 36,…….. Multiples of 8; 8, 16, 24, 32, ……… The first multiples that appear in both is the lowest common multiple. 24 is the LCM of 6 and 8 Highest Common Factor (HCF) • The highest number that can divide into the given numbers. • HINT: Make sure you have listed all the factors of each number Example Find the HCF of 16 and 24 Factors of 16; 1, 2, 4, 8 and 16. Factors of 24; 1, 2, 3, 4, 6, 8, 12 and 24 As you can see 2 and 8 are both common but 8 is the highest common factor. Directed Numbers • 1.Using the line below, simplify the given problems. –8 –7 –6 –5 –4 –3 –2 –1 0 1 2 3 4 • a)10 – 7b) –5 + 2 c) 7 – 12 + 5 5 6 7 8 9 10 11