Question

If two digit number digit at the tens tens place is twice the digit at the unit place if number obtained by interchanging the digit is added to the original number the sum is 66

Answer 1

let the digit at tens place =x
and at ones place be y
so the original digit =10x+y
more over it is given that x=2y
now interchanging the ones and tens digit we get number =10y+x
ATQ
10x+y+10y+x=66
20y+y+10y+2y=66......(x=2y)
33y=66
y=2
so x=2×2=4
so the original number
=10x+y
=40+2
=42

Answer 2

let ones place be = x
so, tens place= 2x

•°•, the original no.= x+10(2x)
the obtained no. by interchanging them
=10(x)+2x

ATQ. x+10(2x) + 10(x)+2x = 66
x+ 20x + 10x + 2x = 66
21x + 12x = 66
33x = 66
x = 66/33 x=2
so, the original no. = 2+10(2×2) = 2+40 =42
and the obtained no. = 10(2)+2(2) = 20+4 = 24