There are infinitely many:
Take any number x and pair it with 10 - x.
The two numbers add up to 10. Every time!
1 and 10, 2 and 5
They all have 10 legs.
The factor pairs of 10 are 1*10, 2*5
All true crabs have 10 legs that are arranged in pairs.
The factor pairs of 20 are pairs of numbers that can be multiplied together to give 20. The factor pairs of 20 are (1, 20), (2, 10), and (4, 5). These pairs represent all the possible combinations of numbers that can be multiplied to equal 20.
1 and 20 2 and 10 4 and 5
1 x 10 and 2 x 5.
4 and 5, 1 and 20, 2 and 10
1 and 20 2 and 10 4 and 5
1 and 20, 2 and 10, 4 and 5
There are 10 factor pairs for 5,000:5000,12500,21250,41000,5625,8500,10250,20200,25125,40100,50
The factor pairs of 20 are: 20,1 / 10,2 / 5,4