Page 50 - Start Up Mathematics_5

• Prime factorization can be done in two ways—factor tree method and division method.
For example, let’s find the prime factorization of 120.

120 2 120
2 60
2 60 2 30

3 15
2 30
5 5

3 10 1

2 5

So, 120 = 2 × 2 × 2 × 3 × 5

1 Write the factors of the following numbers.

(a) 46 (b) 85 (c) 124 (d) 280 (e) 75

2 Write all the prime numbers between 1 and 50.

3 Fill in the blanks.

(a) The first 3 multiples of 16 are ________, ________, ________.

(b) The smallest prime number is ________.
(c) Numbers which are neither prime nor composite are ________ and ________.

(d) The only even prime number is ________.
(e) The factors of 12 are ___________________________________________________.

4 Complete the following table and encircle the common multiples.

20 multiples of 2 10 multiples of 8 10 multiples of 12

(a) Common multiples of 2 and 8 are __________________________________.
(b) Common multiples of 2 and 12 are __________________________________.

(c) Common multiples of 8 and 12 are __________________________________.
(d) Common multiples of 2, 8 and 12 are __________________________________.

5 Write the sixth and the ninth multiples of the following numbers.

(a) 14 (b) 17 (c) 24 (d) 33

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