What will be the product of thousand and units digit of that number ?

Question

A four digit number having all digit successive when substracted by the number formed by using all the digits in reverse pattern (ie reverse of xyz is zyx) gives a four digit number. The sum of all digits of that number is 18.
What will be the product of thousand and units digit of that number ?

Answer 1

four digits are
9876
9876-6789= 3087
sum of digits is 18 = 3+0+8+7 = 18
so
product of thousand and units digit = 3*8 = 24