Question

The sum of the digits of two digit number is 9 the number is 6 times the unit digit find the number

Answer 1

Set t = the tens digit u = the unitis digit t + u = 9 Solve for t by adding -u to each side. t = 9 - u The value of the number is 10t + u. (10t + u) = 6u Substitute (9 - u) for t in the above 10(9 - u) + u = 6u 90 - 10u + u = 6u 90 - 9u = 6u add 9u to each side 90 = 15u divide each side by 15 6 = u since t+u = 9 t + 6 = 9 add -6 to each side t = 3 Since t+u = 9, 3+u = 9 and u = 6 So our number is 36