Question
A number consists of two digits. The sum of the digits is 9. If 45 is subtracted from the number, its digits are interchanged. What is the number?
Options :
63
72
81
90
Answer :
72
Solution :
Let one’s digit is y and ten’s digit is x
Hence the number becomes ‘10x +y’ and the reverse number will be ‘10y+x’
x + y = 9 … (i)
10x + y− 10y − x = 45
x − y = 5 …. (ii)
Adding (i) and (ii)
x = 7
Subtracting (i) and (ii)
y = 2
Therefore the number is 72
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