Question

In a two digit number the units digits is four times the tens digit and the sum of digit is 10. Find the number

Answer 1

Let digit at unit's place be u
digit at ten's place be t

Original number: 10t + 1u
Given that the units digit is four times the tens digit
u = 4t (1)
Also, it is given that the sum of digits is 10
u + t = 10 (2)
Solving Equations (1) and (2) by Substitution method,
Substitute value of u from equation (1) in equation (2),
4t + t = 10
5t = 10
t = 2
Substitute t = 2 in equation (1)
u = 4(2)
u = 8
Hence , the number is 28.