INTRODUCTON
Real numbersinclude rational numbers like positive and negative integers,
fractions, and irrational numbers. In other words, any number that we can
think of, except complex numbers, is a real number. For example, 3, 0, 1.5,
3/2, √5, and so on are real numbers.
Mathematician Richard Dedekind asked these
questions 159 years ago at ETH Zurich, and became
the first person to define real numbers.16 Nov 2017
Mathematician Richard Dedekind asked these questions 159 years
ago at ETH Zurich, and became the first person to define real
numbers.
Every real number can be represented by a different point on the number
line since we know that real numbers can be either rational or irrational. A
real number line, also known as a number line, represents real numbers on
the line with distinct points assigned to each of the numbers.
4.
EUCLID DIVISION LEMMA
Euclid’s division lemma states that given two positive integers a and b, there
exist unique integers q and r such that a = bq + r, where 0 ≤ r < b. This means
that any positive integer a can be divided by another positive integer b, with
a unique quotient q and remainder r.
Dividend = (Divisor × Quotient) + Remainde
An algorithm is a series of well defined steps
which gives a procedure for solving a type of
problem.
The word algorithm comes from the name
of the 9th century Persian mathematician
al-Khwarizmi. In fact, even the word ‘algebra’
is derived from a book, he wrote, called Hisab
al-jabr w’al-muqabala.
A lemma is a proven statement used for
proving another statement.
5.
FUNDAMENTAL THEORM OFARTHEMETIC
In mathematics, the fundamental theorem of arithmetic, also called the
unique factorization theorem and prime factorization theorem, states that
every integer greater than 1 can be represented uniquely as a product of
prime numbers, up to the order of the factors.
Theorem (Fundamental Theorem of Arithmetic) : Every composite number
can be expressed ( factorised ) as a product of primes, and this factorisation is
unique, apart from the order in which the prime factors occur.
6.
REVISITING IRRATIONAL NUMBERS
Theorem: Let p be a prime number. If p divides a, then p divides a, where a is
a positive integer.
An irrational number is a real number that cannot be expressed as a ratio of
integers; for example, √2 is an irrational number. We cannot express any
irrational number in the form of a ratio, such as p/q, where p and q are
integers, q≠0.
EUCLIDS DIVISION ALGORITHM
Euclid’s division algorithm : This is based on Euclid’s division lemma. According
to this,
the HCF of any two positive integers a and b, with a > b, is obtained as follows:
Step 1 : Apply the division lemma to find q and r where a = bq + r, 0 ≤ r < b.
Step 2 : If r = 0, the HCF is b. If r ≠ 0, apply Euclid’s lemma to b and r.
Step 3 : Continue the process till the remainder is zero. The divisor at this
stage will be
HCF (a, b). Also, HCF(a, b) = HCF(b, r).
7.
PROVING √2 ASIRRATIONAL
Let us assume that 2 is a
√ rational number with p and q as co-prime integers and q ≠ 0
⇒ √2 = p/q
On squaring both sides we get,
⇒ 2q2
= p2
⇒ Here, 2q2
is a multiple of 2 and hence it is even. Thus, p2
is an even number. Therefore, p is
also even.
So we can assume that p = 2x where x is an integer.
By substituting this value of p in 2q2
= p2
, we get
⇒ 2q2
= (2x)2
⇒ 2q2
= 4x2
⇒ q2
= 2x2
⇒ q2
is an even number. Therefore, q is also even.
Since p and q both are even numbers, they have 2 as a common multiple which means that p
and q are not co-prime numbers as their HCF is 2.
This leads to the contradiction that root 2 is a rational number in the form of p/q with "p and q
both co-prime numbers" and q ≠ 0.
8.
Revisiting Rational Numbersand Their
Decimal Expansions
Theorem : Let x be a rational number whose decimal expansion terminates.
Then x can be expressed in the form , p/q where p and q are coprime, and the
prime factorisation of q is of the form 2n5mwhere n, m are non-negative
integers.
Theorem : Let x = p/q be a rational number, such that the prime factorisation of
q is of the form 2n 5m, where n, m are non-negative integers. Then x has
decimal expansion which terminates.
Theorem: Let x = p/q be a rational number, such that the prime factorisation of
q is not of the form 2n
5m,
where n, m are non-negative integers. Then, x has a
decimal expansion which is non-terminating repeating (recurring).
9.
SUMMARY
Euclid’s divisionlemma :
Given positive integers a and b, there exist whole numbers q and r
satisfying a = bq + r, 0 ≤ r < b.
The Fundamental Theorem of Arithmetic :
Every composite number can be expressed (factorised) as a product of
primes, and this factorisation is unique, apart from the order in which
the prime factors occur.
If p is a prime and p divides a2, then p divides a, where a is a positive
integer.
10.
MULTIPLE CHOICE QUESTIONS
1)What is the least number that must be added to
1056, so the number is divisible by 23
A)0
B)3
C)2
D)1
Answer: C.
3) The productof a rational and irrational number is
(a) rational
(b) irrational
(c) both of above
(d) none of above
ANSWER:B
4)The sum of a rational and irrational number is
(a) rational
(b) irrational
(c) both of above
(d) none of above
ANSWER:B
13.
5) HCF of8, 9, 25 is
(a) 8
(b) 9
(c) 25
(d) 1
ANSWER: (D)
6)The product of three consecutive positive
integers is divisible by
(a) 4
(b) 6
(c) no common factor
(d) only 1
ANSWER: (B)
14.
7)LCM of thegiven number ‘x’ and ‘y’ where y is a multiple of ‘x’ is given
by
(a) x
(b) y
(c) xy
(d) x/y
ANSWER: (B)
8)The largest number that will divide 398,436 and
542 leaving remainders 7,11 and 15 respectively
is
(a) 17
(b) 11
(c) 34
(d) 45
Answer: (a)
Explanation:(a); [Hint. Algorithm 398 – 7 – 391; 436 – 11
= 425; 542 – 15 = 527; HCF of 391, 425, 527 = 17]
15.
9)There are 312,260 and 156 students in class X, XI
and XII respectively. Buses are to be hired to take
these students to a picnic. Find the maximum
number of students who can sit in a bus if each bus
takes equal number of students
(a) 52
(b) 56
(c) 48
(d) 63
Answer: (a)
Explanation:(a); [Hint. HCF of 312,
260, 156 = 52]
16.
10) There isa circular path around a sports field.
Priya takes 18 minutes to drive one round of the
field. Harish takes 12 minutes. Suppose they both
start at the same point and at the same time and go
in the same direction. After how many minutes will
they meet ?
(a) 36 minutes
(b) 18 minutes
(c) 6 minutes
(d) They will not meet
Answer: (a)
Explanation:(a); [Hint. LCM of 18 and 12 =
36]