S) A two digit number is 3 more than 4 times the sum of its digits. If

1.	S) A two digit number is 3 more than 4 times the sum of its digits. If IS is added to thisnumber, the sum is equal to the number obtained by interchanging the digits. Find thenumber7 ninmsand the total cost of 7 books and 5 pens
Answer» Let the digits be x and y.Thus, number=10x+yNow,(10x+y) - 4(x+y)= 3.....(i)and(10x+y)+ 18=10y+x.....(ii) Solving (i)10x+y-4x-4y=3or,6x-3y=3or,2x-y=1....(1)Solving (ii)10x+y-10y-x=-18or, 9y-9x=18or,y-x=2...(2) (1)+(2)2x-y+y-x=1+2or,x=3Thus, y=x+2 (from (2))y=5Therefore the number= 10x+y=10x3+5=35

S) A two digit number is 3 more than 4 times the sum of its digits. If IS is added to thisnumber, the sum is equal to the number obtained by interchanging the digits. Find thenumber7 ninmsand the total cost of 7 books and 5 pens

Answer»

Let the digits be x and y.Thus, number=10x+yNow,(10x+y) - 4(x+y)= 3.....(i)and(10x+y)+ 18=10y+x.....(ii)

Solving (i)10x+y-4x-4y=3or,6x-3y=3or,2x-y=1....(1)Solving (ii)10x+y-10y-x=-18or, 9y-9x=18or,y-x=2...(2)

(1)+(2)2x-y+y-x=1+2or,x=3Thus, y=x+2 (from (2))y=5Therefore the number= 10x+y=10x3+5=35