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10th Grade > Mathematics

REAL NUMBERS MCQs

Total Questions : 58 | Page 2 of 6 pages
Question 11. Which of the following is not an irrational number?
  1.    √2
  2.    π
  3.    √3
  4.    4.8
 Discuss Question
Answer: Option D. -> 4.8
:
D
2=1.414213562373095..., is non-recurring and non-terminating. So it is an irrational number.
The value of πis 3.14159265358..., the digits neither terminate nor recur and hence it is an irrational number.
3=1.732142857…, is non-recurring and non-terminating. So it is an irrational number..
4.8 = 4810satisfiesall the properties of a rational number. Therefore, it is a rational number.
Question 12. If L.C.M. (150, 100) = 300, then find H.C.F. (150, 100).
  1.    25
  2.    50
  3.    45
  4.    75
 Discuss Question
Answer: Option B. -> 50
:
B
Given: L.C.M. (100,150) = 300
We know that product of two numbers is equal to the product of their HCF and LCM.
Product of numbers 100and 150 = HCF × LCM
100×150 = HCF × 300
HCF = 100×150300
HCF = 15000300
HCF = 50
HCF of 100 and 150 is 50.
Question 13. The largest 4 digit number exactly divisible by 88 is:
  1.    9944
  2.    9988
  3.    9966
  4.    8888
 Discuss Question
Answer: Option A. -> 9944
:
A
We have,
Largest 4-digit number = 9999
88) 9999 (113
9944
-----------
55
When 9999 is divided by 88, remainder is 55.
Required number = (9999 - 55) = 9944
Question 14. There is a circular path around a sports field. Sonia takes 18 minutes to drive one round of the field, while Ravi takes 12 minutes for the same. 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 again at the starting point?
  1.    24
  2.    36
  3.    3
  4.    6
 Discuss Question
Answer: Option B. -> 36
:
B
Number of minutes = LCM of 18 and 12
Prime Factorisation:
12 = 2 ×2 × 3
18 = 2 × 3 × 3
L.C.M of the two numbers = 22×32=36
Question 15. Find the number of prime factors of 5005.
  1.    2
  2.    3
  3.    4
  4.    5
 Discuss Question
Answer: Option C. -> 4
:
C
5005 = 5 × 7 × 11 × 13
There are four prime factors of 5005.
Question 16. The decimal expansion of 141120 will terminate after how many places?
  1.    3
  2.    5
  3.    7
  4.    Will not terminate
 Discuss Question
Answer: Option A. -> 3
:
A
Given rational number 141120
Here, 120=23×3×5
141=3×47
141120 = 3×4723×3×5
=4723×5
Multiply and divide by 52.
=47×5223×5×52
=47×25(2×5)3
=11751000
= 1.175
Therefore, 141120will terminate afterthreedecimal places.
Question 17. Two tankers contain 850 litres and 680 litres of petrol respectively. Find the maximum capacity of a measuring vessel that can be used to exactly measure the petrol from either tankers with no petrol remaining.
  1.    200 litres
  2.    170 litres
  3.    440 litres
  4.    360 litres
 Discuss Question
Answer: Option B. -> 170 litres
:
B
Maximum capacity of the measuring vessel = HCF (850, 680)
We use Euclid's division algorithm to find the HCF of 850 and 680.
850 = 680 × 1 + 170
680 = 170 × 4 + 0
HCF (850, 680) = 170
So, the maximum capacity of the measuring vessel required is 170 litres.
Question 18. Find the HCF and LCM of 90 and 144 by prime factorisation method.
  1.    18 and 720
  2.    720 and 18
  3.    360 and 180
  4.    180 and 720
 Discuss Question
Answer: Option A. -> 18 and 720
:
A
Prime factorisation of 90 and 144:
90=2×3×3×5
144=2×2×2×2×3×3
HCF=2×32=18
LCM=24×32×5=720
HCF and LCM of 90 and 144 are 18 and 720 respectively.
Question 19. Using Euclid's division algorithm, find the HCF of 1650 and 847. 
  1.    10
  2.    11
  3.    12
  4.    27
 Discuss Question
Answer: Option B. -> 11
:
B
Euclid's division algorithm to find HCF of 1650 and 847:
Step 1: 1650 = 847 × 1 + 803
Step 2: 847 = 803 × 1 + 44
Step 3: 803 = 44 × 18 + 11
Step 4: 44 = 11 × 4 + 0
Hence, 11 is the HCF of 1650 and 847.
Question 20. In a seminar, the number of participants for the subjects Hindi, English and Mathematics are 60, 84 and 108 respectively. Find the minimum number of rooms required if in each room the same number of participants are to be seated and all of them are for the same subject.
  1.    7
  2.    14
  3.    21
  4.    28
 Discuss Question
Answer: Option C. -> 21
:
C
Number of rooms will be minimum if each room accomodates maximum number of participants.
In each room, the same number of participants are to be seated and all of them must be for the same subject.
Number of participants in each room must be the HCF of 60, 84 and 108.
Prime factorisation of 60, 84 and 108:
60=22×3×5
84=22×3×7
108=22×33
HCF =22×3=12
In each room, 12 participants can be accommodated.
Number of rooms=Total number of participants12
=60+84+10812
=25212
=21
The total number of rooms is 21.

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