
1 
Find the LCM of 72,108,2100 

A. 
71016 

B. 
37800 

C. 
7460 

D. 
37300 
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Correct answer is : B
Explanation 72= 2^{3} x 3^{3} ,
108= 5^{2} x 7
2100= 2^{2} x 5^{2} x 3 x 7
LCM= 2^{3} x 3^{3} x 5^{2} x 7 = 37800
2 
Find the HCF of 4 x 27 x 3125 , 8 X 9 x 25 x 7 and 16 x 81 x 5 x 11 x 49 . 

A. 
180 

B. 
360 

C. 
540 

D. 
1260 
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Correct answer is : A
Explanation 2^{2} x 3^{3} x 5^{5} ,
2^{3} x 3^{2} x 5^{2} x 7 ,
2^{4} x 3^{4} x 5 x 11 x 7^{2}
To Find the HCF, We have to take the common Prime factors,
here 2, 3 are common and their common powers are:
2^{2} , 3^{2} and 5 .so the HCF is 4 x 9 x 5= 180
3 
The LCM of 24,36,40 is 

A. 
120 

B. 
240 

C. 
360 

D. 
480 
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Correct answer is : C
Explanation 24= 2x2x2x3
36= 2x2x3x3
40= 2x2x2x5
prime factors present are: 2,3,5
Each of these prime factors raised to their highest power is =
2^{3} x 3^{2} x 5 = 360
4 
The number of numberpairs lying between 40 and 100 which has 15 as their HCF is? 

A. 
3 

B. 
4 

C. 
5 

D. 
6 
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Correct answer is : B
Explanation The first number divisible by 15 after 40 is 45.
So, the pairs divisible by 15 are:
45,60
45,75
45,90 (HCF is 30)
then
60, 75
60,90(HCF is 30)
75,90
Hence the remaining pairs with HCF 15 are:
45,60
45,75
60,75
75,90
5 
The H.C.F. of two numbers is 11 and their L.C.M. is 693. If one of the numbers is 77,find the other. 

A. 
80 

B. 
57 

C. 
63 

D. 
99 
See Answer & Explanation
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Correct answer is : C
Explanation Let the required numbers be 15.x and 11x.
Then, their H.C.F. is x. So, x = 13.
The numbers are (15 x 13 and 11 x 13) i.e., 195 and 143.


