Math New Drill : Level 2 SNJ00-0703-L2 Four digit integer of multiple of seven

I make four digit integers using four numbers from 1 to 7. 

I may use the same number any times. 

How many numbers can I make multiple of seven?




Answer
343 pieces

Solution
There are 7 × 7 × 7 = 343 pieces of numbers for thousands, hundreds, and tens digit. 

There is only one number for ones digit to be decided in order for four digit integer to be a multiple of seven. 

Therefore the number of the integer which can be made is 343 × 1 = 343 pieces.