Chapter 9.7, Problem 3P

To determine

To express: the equation expressing the fact.

Answer to Problem 3P

The expression is $10t+u=4t+4u$ .

Explanation of Solution

Given information:

A two-digit number is four times the sum of its digits.

Formula used:

Digit problems are based on our decimal system of numeration.

Step1. The problem asks for the original number.

Step2. Let t = the tens digit of the original number.

Let u = the units digit of the original number.

Step3. Use the facts of the problem to write two equations.

Step4. Solve the equations.

Calculation:

Consider ,

Let t = the tens digit of the original number.

Let u = the units digit of the original number.

	Tens	Units	Value
Original number	t	u	$10t+u$

According to the question,

  $\begin{array}{l}=10t+u=4(t+u)\\ =10t+u=4t+4u\\ \end{array}$

Hence, the expression is $10t+u=4t+4u$ .