Before proceeding to the solution of examples and problems be sure to read the theoretical part of the lesson
Factors and prime numbers
1. Write down all the factors of the following numbers:
17
а) 1; b) 1, 17;
c) 0; d)
1, 13, 17.
2. Write down all the factors of the following
numbers:
26
а) 1,
2, 13, 26;
b) 1,
2, 15, 26;
c) 1, 3, 13, 26;
d) 1,
2, 13, 23.
3. Write down all the factors of the following
numbers:
50
а) 1, 3, 5, 10,
25, 50;
b) 1,
2, 5, 10, 20, 50;
c) 1,
2, 5, 10,
25, 50;
d) 1,
2, 5, 15, 25, 50.
4. Write down the
numbers which are odd numbers:
8, 16,
11, 15, 24,
19, 35, 28,
40, 23, 30,
42, 17, 26,
50.
а) 11, 15,
17, 19, 20, 35;
b) 11, 16, 17, 19,
23, 35;
c) 11,
15, 17, 19, 26, 35;
d) 11,
15, 17, 19,
23, 35.
5. Write down the numbers which are even numbers:
8, 16,
11, 15, 24,
19, 35, 28,
40, 23, 30,
42, 17, 26,
50.
а) 8,
16, 24, 26,
28, 35, 40,
42, 50;
b) 8,
16, 24, 26,
28, 30, 40,
42, 50;
c) 8,
16, 23, 26,
28, 30, 40,
42, 50;
d) 8, 19, 24,
26, 28, 30, 40, 42, 50.
6. Write down the numbers which are prime numbers (this means they have 2
factors only):
8, 16,
11, 15, 24,
19, 35, 28,
40, 23, 30,
42, 17, 26,
50.
а) 11, 17, 19, 23;
b) 11, 15, 19, 23;
c) 11,
17, 19, 26;
d) 11, 16, 19, 23.
7. 1, 2, 4,
5, 10
and 20 are all the factors of which number?
а) 10;
b) 40;
c) 20; d) 60.
8. 1, 2, 11 and 22 are all the factors of which number?
а) 33; b) 22;
c) 44;
d) 11.
9. Which numbers between 20
and 30 have 7 as a factor?
а) 22, 27; b) 23, 28;
c) 21, 29; d) 21, 28.
10. Write down
the next 4 odd numbers after 49?
а) 51,
53, 55, 57;
b) 50, 53, 55, 57;
c) 53, 55, 57, 59;
d) 51,
53, 55.
11. Add together
all the prime numbers less than 20.
а) 79; b) 77;
c) 76; d)
78.
12. Harry picks
his National Lottery numbers by choosing the first six prime numbers. The
winning numbers are drawn as below:
5. 42,
1, 13, 40, 6.
Does Harry win a
small prize for picking 3 correct numbers?
а) ; b) yes;
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