(ii) 28 is a perfect number, since the factors of 2
(1 + 2 + 4 + 7 +14 + 28) = (2 x 28).
EXERCISE 2A
1. Define: (i) factor (ii) multiple. Give five examples of each.
2. Write down all the factors of
(i) 20
(ii) 36
(iii) 60
3. Write the first five multiples of each of the following numbers
(i) 17
(ii) 23
(iii) 65
4. Which of the following numbers are even and which are odd?
(i) 32
(ii) 37
(iii) 50
(v) 69
(vi) 144
(vii) 321
5. What are prime numbers? Give ten examples.
6. Write all the prime numbers between
(i) 10 and 40 (ii) 80 and 100
(iii) 40 and 80
7. (i) Write the smallest prime numh
Answers
Step-by-step explanation:
1.)i) A divisor of an integer, also called a factor of, is an integer that may be multiplied by some integer to produce.
1.)ii) A multiple of a number is a number obtained by multiplying it by a natural number.
2.)factors of 20=2x2x5
factors of 36=2x2x3x3
factors of 60=2x2x3x5
3.)(i) multiple of 17 is 17,34,51,68,85,102,119,136,153, 170,187,204,221,238,255,272,289,306,323,340.
(ii) multiple of 23 is 23,46,69,92,115,138,161,184,207,230,253,276,299,322,345,368,391,414,437,460,483,506,
(iii) multiple of 65 is 65,130,195,260,325,390,455,520,585,650,715,780,845,910,975,1040.
4.)32, 50 and 144 are even numbers
and 37, 69, and 321 are odd numbers
5.)A prime number is a whole number greater than 1 whose only factors are 1 and itself. A factor is a whole number that can be divided evenly into another number. The first few prime numbers are 2, 3, 5, 7, 11, 13, 17, 19, 23 and 29.
6.)(i) prime numbers between 10 and 40 are
11, 13, 17, 19, 23, 29, 31, 37
(ii) prime numbers between 80 and 100
83, 89, 97.
(iii) prime numbers between 40 and 80
41, 43, 47, 53, 59, 61, 67, 71, 73, 79.
7.) 1 is the smallest prime number.
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