# Digits

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## 4/21 Digits

Read the following SAT test question and then select your answer.

Remember to always follow the Knowsys Method to avoid selecting the wrong answer. Read carefully and identify the bottom line, assess your options, attack the problem, and loop back to ensure that what you found is actually what the problem asked for.

The sum of the digits of a three-digit number is 12. If the hundreds digit is 3 times the tens digit and the tens digit is $\frac{1}{2}$ the units digit, what is the tens digit of the number?

First, as always, identify the bottom line.

tens = ?

Next, consider your options. What could you do to solve this problem? What should you do? The best strategy here is to assign a variable to the problem. Say the tens digit is x, and put the rest of the problem in terms of x. You know that the hundreds digit is 3 times the tens digit, so it becomes 3x. The tens digit is also half of the units (ones) digit, so the units digit can be translated 2x.

Finally, the problem says that the sum of the three numbers is 12. Therefore, 3x + x + 2x = 12. Now you just have to solve for x and you will have the value of the tens digit.

3x + x + 2x = 12

6x = 12

x = 2

Look at the answer choices:

A) 2

B) 3

C) 4

D) 6

E) 9

The answer is A.

On sat.collegeboard.org, 58% of responses were correct.

For more help with math, visit www.myknowsys.com!