Form 4 August Holiday Assignment 2024

1. A positive two-digit number is such that the product of the digits is 24. When the digits are reversed, the number formed is greater than the original number by 18. Find the number.



Answer :

To find the two-digit number that meets the given conditions, let's go through the problem step-by-step:

1. Understand the Problem:
- We have a two-digit number where the digits multiply to 24.
- When the digits of this number are reversed, the resultant number is greater than the original number by 18.

2. Setup Variables:
- Let the original number be represented as [tex]\(10a + b\)[/tex] where 'a' is the tens digit and 'b' is the units digit.
- Therefore, the reversed number would be [tex]\(10b + a\)[/tex].

3. Translate Conditions into Equations:
- From the given conditions, we can form the following two algebraic equations:
1. The product of the digits is 24, which can be written as:
[tex]\[ a \times b = 24 \][/tex]
2. When the digits are reversed, the new number is 18 more than the original number:
[tex]\[ 10b + a = 10a + b + 18 \][/tex]

4. Simplify the Second Equation:
- Rearrange [tex]\(10b + a = 10a + b + 18\)[/tex] to get:
[tex]\[ 10b + a - 10a - b = 18 \][/tex]
Simplify to:
[tex]\[ 9b - 9a = 18 \][/tex]
Divide by 9:
[tex]\[ b - a = 2 \][/tex]

5. Solve the System of Equations:
- We now have two equations:
1. [tex]\(a \times b = 24\)[/tex]
2. [tex]\(b - a = 2\)[/tex]

- Solving [tex]\(b - a = 2\)[/tex] for [tex]\(b\)[/tex]:
[tex]\[ b = a + 2 \][/tex]

- Substitute [tex]\(b = a + 2\)[/tex] into [tex]\(a \times b = 24\)[/tex]:
[tex]\[ a \times (a + 2) = 24 \][/tex]
Expand and solve the quadratic equation:
[tex]\[ a^2 + 2a - 24 = 0 \][/tex]

- Factoring the quadratic equation:
[tex]\[ (a + 6)(a - 4) = 0 \][/tex]

- Thus, the solutions for [tex]\(a\)[/tex] are:
[tex]\[ a = -6 \quad \text{or} \quad a = 4 \][/tex]

6. Find Corresponding Values for [tex]\(b\)[/tex]:
- If [tex]\(a = 4\)[/tex], then:
[tex]\[ b = 4 + 2 = 6 \][/tex]

7. Form the Original Number:
- Substituting [tex]\(a = 4\)[/tex] and [tex]\(b = 6\)[/tex] into the original number format [tex]\(10a + b\)[/tex]:
[tex]\[ \text{Original Number} = 10 \times 4 + 6 = 46 \][/tex]

8. Check the Solution:
- The product of the digits is:
[tex]\[ 4 \times 6 = 24 \][/tex]
- The reversed number is [tex]\(64\)[/tex], and [tex]\(64\)[/tex] is indeed [tex]\(18\)[/tex] more than [tex]\(46\)[/tex]:
[tex]\[ 64 - 46 = 18 \][/tex]

Hence, the original two-digit number is [tex]\(46\)[/tex].