Answer with explanation:
⇒Keep in mind
Sum of evens is Even.
Sum of two odd is even.
Sum of the digits from 1 to 5 , when used once =1+2+3+4+5=15
Now, Sum of the digits also can't be 50 when operation Addition is used three times between the numbers or Digits.
45+1+2+3=51
54+....=can't be equal to 50.
43+5+2+1=51
42+5+3+1=51
41+5+2+3=53
Similarly, when number begin from 3, that is 35 +4+......=can;t be equal to 50.
Now, we have to check when operation addition is used twice between digits or numbers can the sum be 50.
That, is sum of two even and one odd or Sum of two odd and one even should be equal to 50.
→As unit place can be filled in two ways that is 2, and 4 and tens place can be filled by remaining of four numbers.
So, total number of even numbers using the digits 1,2,3,4,and 5 =4 ×2=8
These numbers are, 12,32,42,52,14,24,34,and 54.
→And total number of numbers which are odd using the digits 1,2,3,4,and 5 are=4 ×3=12, which are, 21,31,41,51,13,23,43,53,15,25,35,45.
When you take any of these two,two digit numbers between these 20 numbers and combine with another distinct remaining digit ,it can't be equal to 50.
For example:
→ 12 +34+5≠50
→14+35+2≠50
→21+24+5≠50