a plate 3 digit # . the prod. of the dig. is 210, the sum is 18, and the # is in descending form, whats the #?

Answer 1

210 = 2 * 3 * 5 * 7

You need to group two of these factors, but they can't be more than 10. 2*5 and 2*7 don't work, so you must group 2 and 3 to get 6. So your factors are 7, 6 and 5 (in descending order).

So the only way you can make this plate is 765

7+6+5 = 18
7*6*5 = 210

Answer 2

Let the # is abc
axbxc=210 & a+b+c=18
210=21x10=7x3x5x2=7x6x5
18=7+6+5
i.e.abc=765
i.e. # is 765