A) 21
B) 24
C) 36
D) 42
Correct Answer: A
Solution :
Let the unit digit of the number be x and tens digit be y. Number \[=10y+x\] According to the question, \[x+y=10\] ... (i) and \[10x+y=(10y+x)-36\] \[\Rightarrow \] \[~10x+y-10y-x=-36\] \[\Rightarrow \] \[9x-9y=-36\]\[\Rightarrow \]\[xy=-4\] ... (ii) Now, on solving equation (i) and (ii), we get \[x=3\] and \[y=7\] \[\therefore \] Required product of two digits \[=3\times 7=21\]You need to login to perform this action.
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