A number consist of two digit whose product is 30. if unit's digit is subtracted from ten's digit, 1 is obtained,find the number.

let unit digit=X

Therfor ten's digit=X+1

now, X*(X+1)=30

or, X^2+X-30=0

or, X^2+6X-5X-30=0

or, X(X+6)-5(X+6)=0

or, (X-5)(X+6)=0

or, X=5 or -6

 

X can not be -6.

ther for X=5

X+1=6

 

Therfor, number=65