Question

Consider s=(1,2,3...10). In how many ways two numbers can be selected from s so that sum of selected is a double digit number ?

Answer 1

Answer:

32

Step-by-step explanation:

1,10; 2,10; 3,10; 4,10; 5,10; 6,10; 7,10; 8,10; 9,10; 10,10

1,9; 2,9; 3,9; 4,9; 5,9; 6,9; 7,9; 8,9; 9,9;

2,8; 3,8; 4,8; 5,8; 6,8; 7,8; 8,8;

3,7; 4,7; 5,7; 6,7;

4,6; 5,6

Answer 2

Answer:

29

Step-by-step explanation:

If the sum is a two-digit number, then both the values simultaneously cannot be less than 5. Now, start making the sets by taking different values greater than or equal to at least one of the numbers.