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Q.

Using prime factorization, the HCF and LCM of 21, 28, 36, 45 is:


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a

H.C.F = 3 and L.C.M = 1280

b

H.C.F = 1 and L.C.M = 1260

c

H.C.F = 2 and L.C.M = 1220

d

H.C.F = 5 and L.C.M = 1250 

answer is B.

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Detailed Solution

Given 4 numbers 21, 28, 36 and 45.
The prime factors are,
21=3×7 28=2×2×7 36=2×2×3×3 45=3×3×5
As, the common factor is 1, H.C.F = 1.
Now, the L.C.M of 21, 28, 36, 45 is,
= 2 2 × 3 2 ×5×7 =1260
Therefore, H.C.F = 1 and L.C.M = 1260.
Hence, option 2 is correct.
 
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