Math Problem Statement

The sum of the digits of a two-digit counting number is 5. When the digits are reserved, the new number is 27 greater than the original number. What are the two numbers?

Solution

Let's define the two-digit number as 10a+b10a + b, where aa is the tens digit and bb is the units digit.

We are given two conditions:

  1. The sum of the digits is 5: a+b=5a + b = 5

  2. When the digits are reversed, the new number is 27 greater than the original number: 10b+a=10a+b+2710b + a = 10a + b + 27

Step 1: Simplify the second equation

Start by simplifying the second equation: 10b+a=10a+b+2710b + a = 10a + b + 27 Subtract bb and aa from both sides: 9b9a=279b - 9a = 27 Now, divide through by 9: ba=3b - a = 3

Step 2: Solve the system of equations

Now we have a system of two equations:

  1. a+b=5a + b = 5
  2. ba=3b - a = 3

Add the two equations together to eliminate aa: (a+b)+(ba)=5+3(a + b) + (b - a) = 5 + 3 2b=82b = 8 b=4b = 4

Step 3: Find aa

Substitute b=4b = 4 into the first equation: a+4=5a + 4 = 5 a=1a = 1

Final Answer:

The original number is 10a+b=10(1)+4=1410a + b = 10(1) + 4 = 14, and the reversed number is 10b+a=10(4)+1=4110b + a = 10(4) + 1 = 41.

Thus, the two numbers are 1414 and 4141.

Would you like further details on any step?

Here are five related questions to explore:

  1. What happens if the sum of the digits is 7 instead of 5?
  2. How does the equation change if the new number is 35 greater than the original?
  3. What if the digits differ by 4 instead of 3?
  4. Can you generalize the method for any two-digit number where the digits are reversed?
  5. What if the number is three digits instead of two?

Tip: When working with digit-related problems, translating the digits into algebraic terms (like 10a+b10a + b) can make the relationships between numbers easier to work with.

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Math Problem Analysis

Mathematical Concepts

Algebra
Systems of Linear Equations
Digit Problems

Formulas

a + b = 5
b - a = 3
10a + b for two-digit number representation

Theorems

Basic properties of linear equations
Digit reversal in a two-digit number

Suitable Grade Level

Grades 6-8