Math Problem Statement

In a two-digit number, the tens digit exceeds the units digit by 1, and the product of the digits is 30. Find the number.

Solution

Let’s analyze the question from the uploaded image. The problem is as follows:


"In a two-digit number, the tens digit exceeds the units digit by 1, and the product of the digits is 30. Find the number."


Solution:

Let the tens digit be xx and the units digit be yy.

Step 1: Form the equations

  1. The tens digit exceeds the units digit by 1: x=y+1x = y + 1

  2. The product of the digits is 30: xy=30x \cdot y = 30

Step 2: Substitute x=y+1x = y + 1 into xy=30x \cdot y = 30

Replace xx in the second equation: (y+1)y=30(y + 1) \cdot y = 30

Expand the equation: y2+y=30y^2 + y = 30

Rearrange into standard quadratic form: y2+y30=0y^2 + y - 30 = 0

Step 3: Solve the quadratic equation

Use the quadratic formula: y=b±b24ac2ay = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} Here, a=1a = 1, b=1b = 1, and c=30c = -30. Substitute into the formula: y=1±124(1)(30)2(1)y = \frac{-1 \pm \sqrt{1^2 - 4(1)(-30)}}{2(1)} y=1±1+1202y = \frac{-1 \pm \sqrt{1 + 120}}{2} y=1±1212y = \frac{-1 \pm \sqrt{121}}{2} y=1±112y = \frac{-1 \pm 11}{2}

Solve for the two possible values of yy: y=1+112=5ory=1112=6y = \frac{-1 + 11}{2} = 5 \quad \text{or} \quad y = \frac{-1 - 11}{2} = -6

Since yy must be a positive digit, y=5y = 5.

Step 4: Find xx

Using x=y+1x = y + 1: x=5+1=6x = 5 + 1 = 6

Step 5: Form the number

The two-digit number is: 65\boxed{65}


Would you like a detailed verification or further explanation?

Related Questions:

  1. What if the product of the digits was 56 instead of 30? What would the number be?
  2. What are the possible two-digit numbers where the digits differ by 1?
  3. How would the solution change if the product of the digits was negative?
  4. Can you generalize this problem for xy=kx - y = k and xy=px \cdot y = p?
  5. What happens if both digits are the same? Can such a case satisfy similar conditions?

Tip:

For problems involving digits, define them as variables and build equations based on their relationships (e.g., sum, difference, or product).

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Digit Problems

Formulas

Quadratic formula: x = (-b ± √(b² - 4ac)) / 2a

Theorems

Properties of quadratic equations
Basic number theory for digits

Suitable Grade Level

Grade 8-10