Question

What is the greatest number which can be made using each of the digits 5,3,1,4,7

Answer 1

That is tricky but I multiplied them all and got 420 I hope that helps. :)

Answer 2

Just start with the biggest number to the smallest
order from largest to samllest
7,5,4,3,1

the number is 75,431
if you wanted to use other things
$431^{75}$ would be pretty big

but 75,431! would be large as well