Question

दो अंकों की एक संख्या अपने अंकों के योग की 7 गुनी है।। इससंख्या
को पलटने से बनी संख्या मूल संख्या से 18 कम है। यह संख्या है: ।
(a) 42
(b) 52
(c) 62
(d) 24

8. (a)​

Answer 1

Answer:

a. 42

Step-by-step explanation:

let no. 10x+y

1equation=10 x+y=7(x+y)=10x +y-7x-7y

3x-6y=0

x-2y=0first equqtion

10y+x=10x+y-18

x-y=2second equation

sub first and second equation

x-2y-x+y=-2

-y=-2

y=2

take y=2

x-y=2

x-2=2

x=2+2

x=4

then number is 10x+y

10*4+2

40+2=42

Answer 2

Answer:

42

Step-by-step explanation:

let the digit at tens place = x

and the digit at ones place = y

then the no. will be = 10x +y

according to question

7(x+y) = (10x+y)

7x + 7y = 10x + y

10x -7x = 7y -y

3x = 6y

x = 2y

on reversing the digits new no. will be

10y + x

it is given that

10y +x = (10x +y) -18

on substituting

x=2y

we get

10y +2y = 10 (2y) +y -18

12y = 21y -18

21y -12y = 18

9y = 18

y= 2

x= 2y

x= 2×2

= 4

the no. = 10x + y

= 10(4) + 2

= 40+ 2

= 42