Question

A number consists of two digits whose sum is 9.If 9 is subtracted from the number, the digits interchange their places. Find the number.

Answer 1

$\mathfrak{hello}$

◆here is your answer ..

let us assume that two digits are x and y

● so two digit number=10x+y
● when we interchange we get =10y+x

Given in question:
x+y=9
y=9-x --------(1.)

A/q.
10x+y-9=10y+x .. ... put y=9-x
10x+(9-x)-9=10(9-x)+x
10x+9-x-9=90-10x+x
10x-x+9-9=90-9x
9x=90-9x
9x+9x=90
18x=90
$x = \frac{90}{18} \\ \\ x = 5$

y=9-x
put value of x in eq(1.)
y=9-5
y=4

so the two digit number
=10x+y
=10(5)+4
=50+4
=54

$\bold{\underline{so\:2\: digit\:numer\:is\:54}}$

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hope it helps you. (^o^)
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