2 two digit numbers chosen in such a way that all 4 digits used are distinct, are such that their sum is 90. How many such pairs are possible if in both numbers units place is 1 more than tens place.
OPtion
1) 1
2) 2
3) 3
4) 4
5) 5
6) 6
7) 7
8) 8
9) 9
10)0
Solution
Let given number are
10x + (x+1) and 10y + (y+1)
then as given
10x + (x + 1) + 10y + (y + 1) = 90
11x + 11y = 88
x + y = 8
So 12 & 78, 23 & 67, 34 & 56.
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