Question

The sum of the two digits of a number is 9. If the tens digit is one-half the units digit, what is the number?

Let t = the tens digit, u = the units digit, and t + u = 9. Which of the following equations would complete the system?

Answer 1

Answer: correct answer is t=1/2u

Explanation:

Answer 2

`t=(u)/(2)` would complete the system

Number is 36

Explanation:

Let t = the tens digit, u = the units digit

We have the sum of the two digits of a number is 9

t + u = 9

We also have the tens digit is one-half the units digit

`t=(u)/(2)`

Substituting

`(u)/(2)+u=9\\\\(3u)/(2)=9\\\\u=6`

t + 6 = 9

t = 3

So the number is 36.