Mathematics
In a 2-digit number ab and a > b then ab - ba is equal to :
0
9(a - b)
9(b - a)
none of these
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Answer
ab - ba
= (10a + b) - (10b + a)
= 10a + b - 10b - a
= (10a - a) + (b - 10 x b)
= 9a - 9 x b
= 9(a - b)
Hence, option 2 is the correct option.
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