Pairs of natural numbers whose least common multiple is 78 and the gre...
Let the no.s be a & b,
GCD [ a , b ] = 13;
=> Let a = 13m and b = 13n
Now, LCM [ a , b ] = 78
=> 13m | 78
=> m | 6 and similarly, n | 6; --> Also, m does not divide n
.'. Possible values of (m,n) are :->
--> [ 1 , 6 ] , [ 2 , 3 ]
.'. Possible values for ( a , b ) are :-> [ 13 , 78 ] , [ 26 , 39 ]
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Pairs of natural numbers whose least common multiple is 78 and the gre...
Solution:
Given, LCM = 78 and GCD = 13
Let the required pair of numbers be a and b.
Therefore, a × b = LCM × GCD
=> a × b = 78 × 13
=> a × b = 1014
Now, we need to find the pair of natural numbers whose product is 1014.
Prime factorizing 1014, we get:
1014 = 2 × 3 × 13 × 13
Hence, the only possible pairs of natural numbers whose product is 1014 are:
(2, 507), (3, 338), (6, 169), (13, 78), (18, 57), (26, 39)
Out of these pairs, we need to find the pair whose GCD is 13.
Let's check each pair:
- (2, 507) => GCD = 1
- (3, 338) => GCD = 1
- (6, 169) => GCD = 1
- (13, 78) => GCD = 13
- (18, 57) => GCD = 3
- (26, 39) => GCD = 13
Hence, the possible pairs of natural numbers whose LCM is 78 and GCD is 13 are (13, 78) and (26, 39).
Therefore, the correct answer is option 'D': 78 and 13 or 26 and 39.
Pairs of natural numbers whose least common multiple is 78 and the gre...
D
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