Question

¿ a two digit number is 4 times the sum of its digit. if 18 is added to the number ,the digits are reversed find the number?
========>answer is 24<=======
u can solve in ur copy

Answer 1

Hey!!!

Good Afternoon

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let the ten's digit be x and unit digit be y.

Then ATQ,

=> 10x + y = 4(x + y)

=> 10x + y = 4x + 4y

=> 6x - 3y = 0

=> 2x - y = 0 --------(1)

Also

=> 10x + y + 18 = 10y + x

=> 9x - 9y = -18

=> x - y = -2 -------(2)

Subtract (2) from (1)

=> 2x - y - (x - y) = 0 - (-2)

=> 2x - y - x + y = 2

=> x = 2

This using x in (1)

=> 2(2) - y = 0

=> y = 4

Thus original number = 20 + 4

=> 24

Thus the number is 24

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Hope this helps ✌️

Happy Mother's Day :-)

Answer 2

hi

let the number be xy

tens digit = 10x and ones digit = y

a two digit number is 4 times the sum of its digit

=> 10x+y = 4(x+Y)

=>10x+y = 4x +4y

=>10x - 4x = -y +4y

=>6x = 3y

=>let us divide by 3

=>y = 2x

if 18 is added to the number ,the digits are reversed 

=> [10x+Y] +18 = 10y +x

since y is 2x

=>[10x+Y] +18 = 10y +x

=>[10x+2x] +18 = 10(2x) +x

=>12x +18 = 20x +x

=> 12x +18 = 21x

=>18 = 21x - 12x

=>18 = 9x

=>x = 18/9

=>x = 2

sine y = 2x

=>2*2

=>4

origibnal no. = xy

since xis 2 and y is4

=>24

hope it helps u

:)