Discrete Math Chapter Relations and FunctionsSolutionLet BN

Discrete Math. Chapter: Relations and Functions.

Solution

Let, |B|=N

SO, each element of A must map to a different element in B

SO, 1 can map to N elements

2 to N-1

3 to N-2

4 to N-3

and 5 to N-4

So, 6720 is product of 5 consecutive natural numbers

6720=64*3*5*7=16*4*3*5*7=4*6*5*7*8=4*5*6*7*8

So we have expressed 6720 as prodcut of 5 consecutive integers

So, N=8

HEnce, |B|=8