Question

Sum of two digit is 7 the number obtained by interchanging the digits is twice the number

Answer 1

Answer:

the original no. is 25

Step-by-step explanation:

let tens place digit =x

let ones place digit=y

the original no.=10x+y(any numbers expanded form looks like this for example 23=2*10+3)

the reversed no.is =10y+x

according to the question,

2(10x+y)=10y+x

x+y=7-----2

from equation2 we get the value of y(ones place digit)in terms of x)

which is y=7-x

now we will place it in the first equation like this,but before we do this we should simplify the equation1

2(10x+y)+2=10y+x

10x+y+10x+y+2=10y+x

20x+2y+2=10y+x

20x-x+2=10y-2y

19x+2=8y

we will now put the value of y in this equation,

19x+2=8(7-x)

19x+2=8(7-x)

19x+2=56-8x

19x+8x=56-2

27x=54

x=2

now we know the value of x so we can easily find the value of y,

in equation 2 by putting the value of x we can get the value of y

7-x=y

7-2=y

y=5

thus the original no is 25