Question

plz solve the question no.15

Answer 1

Seven times a given two digit number is equal to four times the number obtained by inter changing the digits
7(10x+y)=4(x+10y)
70x+7y=4x+40y
66x-33y=0
2x-y=0
2x=y
The difference of the digits is 3
y-x=3
2x-x=3
x=3
y=6
that number is 36.

Answer 2

let the digit at unit place is y
digit at tens place is x

According to question

7(10x + y) = 4(10y + x)
70x + 7y = 40y + 4x
66x = 33y
=> y = 2x. ------(1)

and, y - x = 3

put value from eq(1)

2x - x = 3

x= 3

and y = 2x = 2*3 = 6

x = 3 and y = 6

The number is 10x+y = 10*3 + 6 = 36

Hope it helps
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