Question

please answer this!!!!

Answer 1

let the one's digit be y and ten's digit be x
then the no is 10x+y
acc/que
product of the digit is 20
=x×y=20
=x=20/y. -1
if 9 is added to the no then the digit interchange
= 10x+y+9=10y+x
9x=9y-9
= x=y-1. -2
now putting the value of x in eq. 2 from eq.1
20/y=y-1
20/y-y =-1
20-y²=-y
y²-y-20=0
y²-5y+4y-20=0
y(y-5)+4(y-5)=0
(y+4)(y-5)=0
y= -4 or y=5
y cannot be -ve so y =5
now putting the value of y in eq.2
x=5-1
x=4
therefore the no is= 10×4+5
=45 (ans
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