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# Number

### Natural Numbers:

The natural numbers include whole numbers except 0.

E.g. 1,2,3,4,5,6…

### Integers:

Positive natural numbers, negative natural numbers along with 0 are called integers.

-1,-2,-3,0,+1,+2,+3…

### Prime Numbers:

A prime number is a number with exactly two factors (i.e. 1 and itself (1×3))

E.g. 2,3,5,7,111,13,17,19,23,29,31…

### Composite Numbers:

Those numbers which have more than two factors.

E.g. 4,6,8,9,10,12,14,15,16,18,20…

### Factors:

The factors of a number are the natural numbers which divide exactly into that number (without a remainder).

8:  1×8             12:  1×12

2×4                     2×6

3×4

### Multiples:

Multiples of a number are numbers in its times table.

Multiples of 5 are 5, 10, 15, 20, 25, 30…

### Highest Common Factor (HCF):

It is the highest factor which is common to all of the given numbers.

E.g.  8:  1×8                 12:  1×12

4                          2×6               In this example the common factors are 1, 2, 4 and the

4                Highest factor is 4; therefore the HCF of 12 and 8 is 4.

In this example the common factors are 1, 2, 4 and the highest factor is 4; therefore the HCF of 12 and 8 is 4.

### Rational Number:

A rational number is one which can be expressed in the form where a and b are integers and b is not equals to 0. ### Irrational Number:

Numbers that can’t be expressed as as a fraction or a ratio of 2 integers are known as irrational numbers. ### Real Numbers:

These include all rational, irrational, fractions and integers.

### Terminating Decimals:

These are decimal numbers which stop after a certain number of decimal places.

E.g. 7/8 = 0.875 it stops after three decimal places.

### Recurring Decimals:

These are decimal numbers which keep repeating a digit or a group of digits.

E.g. 137/259 = 0.528 957 528 957 528 957… the six digits 528 957 repeat in this order.

### Even Number:

Numbers which are divisible by 2

E.g. 2, 4, 6, 8…

### Odd Number:

Numbers which are not divisible by 2

E.g. 1, 3, 5, 7

### Square Number:

It is the result of multiplying  a number by itself.

E.g. 12, 22, 32 ….. 1, 4, 9….

### Cube Number:

It is the result of multiplying a number by itself 3 times.

E.g. 13, 23, 33 …. 1, 8, 27….

### Significant Figures:

The following are few examples showing clearly what is meant by significant figures.

8064 = 8000 (correct to 1 significant figures)

8064 = 8100 (correct to 2 significant figures)

8064 = 8060 (correct to 3 significant figures)

0.00208 = 0.005 (correct to 1 significant figures)

0.00208 = 0.0021 (correct to 2 significant figures)

3.00508 = 3.01 (correct to 3 significant figures)

### Decimal Places:

The following are few examples showing clearly what is meant by decimal places.

0.0647 = 0.1 (correct to 1 dp)

0.0647 = 0.06 (correct to 2dp)

0.0647 = 0.065 (correct to 3dp)

2.0647 = 2.065 (correct to 3dp)

### Test Of Divisibility: Relax your Mind From Studying and WATCH this Beautiful Sun Flower Painting.

SUBSCRIBE to learn How to Paint 1. Interested in learning Maths, English Language and Economics at IGCSE OLevel to write in November 2017. After that, l would like to study A Level English Literature and Economics.May l ask for your help in studying and passing my exams?

2. x is an integer between 50-70
(A) x is a cube
(B)x is prime factor of 268

• Hey Owais, the answer for part (A) is 64 and for part (B) is 67

3. • 4. 