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9th Grade > Mathematics

NUMBER SYSTEMS MCQs

Total Questions : 197 | Page 1 of 20 pages
Question 1. 1.666666...... is a rational number and can be expressed in pq form. Then p + q is ______.
  1.    9
  2.    6
  3.    7
  4.    8
 Discuss Question
Answer: Option D. -> 8
:
D
Let x= 1.6666...... ----- (i)
then, 10x= 16.666666 ----- (ii)
Subtracting (i) from (ii), we get
10x - x = (16.666666...) - (1.666666...)
9x = 15
Hence x = 159=15393=53
i.e., p = 5 and q = 3
So, p + q = 8.
Question 2. 1417×1417 can be represented as ___________.
  1.    1417+17
  2.    (142)17
  3.    (14×14)17
  4.    All of the above
 Discuss Question
Answer: Option D. -> All of the above
:
D
For any positive real number 'a' and integers 'm' and 'n', we define
1.
am×an=am+n
2. (am)n=amn
3. (ab)m=ambm andifa=b, the expression becomes (a×a)m=(a2)m=a2m.
​​​​​​So, using first rule, we have
1417+17=1427
Now, using secondrule,
(142)17= 1427
Finally, using thirdrule,
(14×14)17=1427
Hence, we see that all the three results are same.
Question 3. Find the value of (2+2)(22).
  1.    0
  2.    1
  3.    2
  4.    3
 Discuss Question
Answer: Option A. -> 0
:
A
A common tendency to solve this question is to apply the algebraic identity (a2b2)=(a+b)(ab). But by observation, we can see that (22), which is one of the factors, will result in 0, thus making the final value of the whole expression as 0 i.e.
(2+2)(22)
=(2+2)×(0)

=0
Question 4. If 14.287628762876........ can be represented in pq form, then 'p - q ' is ________.
  1.    132863
  2.    142862
  3.    142876
  4.    142863
 Discuss Question
Answer: Option A. -> 132863
:
A
Let 'x' = 14.287628762876 -------(i)
then 10000x = 142876.287628762876 --------(ii)
Subtracting (i) from (ii) we get
10000x - x =142876.287628762876 -14.287628762876
9999x = 142862
then 'x' = 1428629999
p = 142862, q = 9999
So, p-q = 132863
Question 5. A number xwas found to be represented in the simplest pq form. The decimal expansion of this number was found to be 5.3333333333..... Find the value of p - q.
  1.    11
  2.    12
  3.    13
  4.    14
 Discuss Question
Answer: Option C. -> 13
:
C
Given decimal is5.3333333......
Let, x=5.3333333......
Therefore, 10x=53.33333333....
Subtracting x from 10x, we get
10xx=53.33333..5.33333..=48
9x=48
x=489=163=pq
So, pq=163
pq=13
Question 6. Which of the following represents whole numbers?
  1.    Positive integers
  2.    Negative integers
  3.    π
  4.    Integers
 Discuss Question
Answer: Option A. -> Positive integers
:
A
Integers are constituted by natural numbers, their negatives and 0. Removing the negative numbers from integers would leave us with the whole numbers. Therefore, whole numbers include 0 as well as all the positive integers.
Question 7. The expression 535+3 when simplified reduces to a-b15.
Then a + b is __________.
  1.    15
  2.    10
  3.    20
  4.    5
 Discuss Question
Answer: Option D. -> 5
:
D
In 535+3, the denominator has to be rationalised for simplification. So ,
535+3×5353
=(53)25232
=12[(5)2+(3)2215]
=415
So, a=4 and b=1.
a + b = 4 + 1 = 5
Question 8.   is neither a positive nor a negative integer.
 Discuss Question

:
The integers include positive integers i.e. 1, 2, 3, ... , negative integers i.e. -1, -2, -3, ... and zero. Hence, zero isneither a positive nor a negative integer.
Question 9. 34 lies between 12 and 1.
  1.    True
  2.    False
 Discuss Question
Answer: Option A. -> True
:
A
To check if a number lies between any two numbers, we first convert the numbers into the decimal form. 34=0.75 ,12=0.5 and we have to check if 0.75 lies between 0.5 and 1 and plot the numbers on the number line as follows :
34 Lies Between 12 And 1.
Therefore, we can say that34 lies between 12 and 1.
Question 10. Which of the following is an irrational number?
  1.    14.287628762876.....
  2.    15.2323232323......
  3.    5.2731687143725186.....
  4.    1.33333333...
 Discuss Question
Answer: Option C. -> 5.2731687143725186.....
:
C
Irrational numbers are defined as those numbers which havea non-terminating and non-repeating decimal expansion and hence cannot be represented in the pqform. So, here we see that out of the given options the number 5.2731687143725186..... has a non-terminating and non-repeating decimal expansion as clearly one can interpret that there are no patterns formed in the decimal expansion and the number goes on expanding arbitrarily.

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