Math Problem Statement

A number consists of two digits of which the ten's digit exceeds the unit digit by 7.The number itself is equal to 10 times the sum of the digits. Find the number

Solution

Let the two-digit number be represented as 10a+b10a + b, where aa is the ten's digit and bb is the unit digit.

We are given two conditions:

  1. The ten's digit exceeds the unit digit by 7:
    a=b+7a = b + 7

  2. The number itself is equal to 10 times the sum of the digits:
    10a+b=10(a+b)10a + b = 10(a + b)

Step 1: Simplify the second equation

We can expand and simplify the second condition: 10a+b=10a+10b10a + b = 10a + 10b Subtract 10a10a from both sides: b=10bb = 10b Subtract bb from both sides: 0=9b0 = 9b Thus, b=0b = 0.

Step 2: Substitute b=0b = 0 into the first equation

From the first condition a=b+7a = b + 7, substituting b=0b = 0: a=0+7=7a = 0 + 7 = 7

Step 3: Form the number

The number is 10a+b=10(7)+0=7010a + b = 10(7) + 0 = 70.

Thus, the number is 70\boxed{70}.

Would you like more details on any part of the solution?

Here are 5 related questions:

  1. What if the ten's digit exceeds the unit digit by a different value?
  2. How would the solution change if the sum of the digits was doubled?
  3. Can you generalize a formula for such problems involving digit relations?
  4. How many other two-digit numbers satisfy different similar conditions?
  5. What happens if we reverse the digits of the number found?

Tip: Always check your solution by plugging values back into the original conditions to ensure accuracy.

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Math Problem Analysis

Mathematical Concepts

Algebra
Number Properties
Linear Equations

Formulas

10a + b = 10(a + b)
a = b + 7

Theorems

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Suitable Grade Level

Grades 6-8