I guess 4 paris are possible
We know that hcf is higest common factor in both numbers which is 20 here. Both numbers will be multiple of 20.
remaining factors of the numbers is 800/20 = 40
we just need to distribute the prime factors (2*2*2*5) of 40 to both numbers with 20.
supoose both numebrs are A and B
A |
B |
2 *20 =40 |
2*2*5*20 =400 |
5*20=100 |
2*2*2*20 =160 |
2*2*20=80 |
2*5*20=200 |
2*2*2*5*20 =800 |
1*20=20 |
A*B =LCM * HCF = 800*20 = 16000