The LCM of two numbers x and y is 20. Find the number of unordered pairs (x,y)?
1). 8
2). 9
3). 7
4). 10
The pairs of numbers are (1,20), (2,20), (4,20) , (5,20) , (10,20) , (20,20) , (4,5) , (4,10). So, the number of unordered pairs is 8.
The pairs of numbers are (1,20), (2,20), (4,20) , (5,20) , (10,20) , (20,20) , (4,5) , (4,10). So, the number of unordered pairs is 8.