Quandaries and Queries
  

 

I can't figure this out, The question is

Find the greatest possible difference of two 3-digit numbers that use the digits 3, 5, 7 and 9 only once in each number.

The teacher says the answer is 62 but I can't figure out how she did it. Can you help.

Melissa
 

 

Hi Melissa,

I don't think I understand the problem since 975 and 357 are two 3-digit numbers that use the digits 3, 5, 7 and 9 only once in each number and

975 - 357 = 618

Penny

Claude found the problem.

I can do
Find the greatest possible difference of two 2-digit numbers that use the digits 3, 5, 7 and 9 only once in each number.

97 - 35 = 62.

The tens contribute the most to the difference so I select 9 (the largest choice) as the tens digit of the largest number and 3 (the smallest) as the tens digit of the smallest number. I then select the largest remaining number (7) as the units digit of the largest number, and the remaining (5) as units digit of the smaller number.

Claude