The digit in the tens place of a number consisting of two digits is greater than that in the units - Maths - Pair of Linear Equations in Two Variables

Question

The digit in the tens place of a number consisting of two digits is
greater than that in the units place by 7 The sum of digits 1/9th
of the number Find the number

Varun Rawat · Accepted Answer

Let the digit at units place = xLet the digit at tens place = yNow, original number = 10y + xNow, according to first condition :y = x + 7     
1according to second condition :x + y = 1910y + x⇒9x + 9y = 10y + x⇒y = 8x    
2From 1 and 2, we get8x = x + 7⇒7x = 7⇒x = 1Now, from 1, we gety = 1 + 7 = 8Now, original number = 10 × 8 + 1 = 81

The digit in the tens place of a number consisting of two digits is greater than that in the units place by 7.The sum of digits 1/9th of the number.Find the number.