Q. 143.7( 21 Votes )
A two - digit number is 3 more than 4 times the sum of its digits. If 18 is added to the number, the digits are reversed. Find the number.
Let the two - digit number be xy (i.e. 10x + y).
After reversing the digits of the number xy, the new number becomes yx (i.e. 10y + x).
According to question -
(10x + y) = 4(x + y) + 3
⇒ 6x - 3y = 3
⇒ 2x - y = 1.....(1)
(10x + y) + 18 = (10y + x)
⇒ 9x - 9y = - 18
⇒ x - y = - 2.....(2)
Subtracting equation (2) from (1), we get -
x = 3
Substitute the value of x in equation (1), we get -
y = 5
Thus, the required number is 35.
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Solve the following pair of linear equation by cross - multiplication method:
x + 4y + 9 = 0
5x – 1 = 3yKC Sinha - Mathematics
Solve each of the following systems of equations by using the method of cross multiplication:
2x + y = 35, 3x + 4y = 65.RS Aggarwal - Mathematics