Maths

[Barnsey2]

For the mathematic genius among you, given numbers
1 to 30 how many combinations of these numbers in sets of two, i.e. doubles does it take to cover all combinations.
Thanks in advance, my abacus is broken.

[lajohn]

use your fingers and toes. those should be enough.

[glasman]

29+28+27.........................+1.
You can do the rest yourself.

[crofter]

There are 30x29/2 combinations (= 435) where numbers are different and the order is not important.

Taking into account the order of selection, there are 30x29 permutations (= 870).

If the numbers can be the same (ie doubles allowed) then there are 30x30 = 900 ordered number pairs.