I roll a die four times.
Four numbers of spots are arranged in order and a number of four figures is made.
How many numbers of the number which includes just three same numbers in any three digits of four figures are made?
Answer
120 pieces
Solution
The number which becomes the three same numbers is six kinds from 1 to 6.
When 1 is the number of three, one more number is five kinds from 2 to 6.
One more number is set to 2.
There are 4 kinds of four figures which are 1112, 1121, 1211, and 2111.
Therefore, there are 6 × 5 × 4 = 120 pieces in all.
Four numbers of spots are arranged in order and a number of four figures is made.
How many numbers of the number which includes just three same numbers in any three digits of four figures are made?
Answer
120 pieces
Solution
The number which becomes the three same numbers is six kinds from 1 to 6.
When 1 is the number of three, one more number is five kinds from 2 to 6.
One more number is set to 2.
There are 4 kinds of four figures which are 1112, 1121, 1211, and 2111.
Therefore, there are 6 × 5 × 4 = 120 pieces in all.
