Permutations & Combinations
Grade 11
Question:
<p>Number of four-digit number between 5000 and 6000 such that the thousand’s digit is equal to the sum of the other three-digit, is:</p>
<p style="display:inline">21</p>
<p style="display:inline">30</p>
<p style="display:inline">42</p>
<p style="display:inline">15</p>
Step-by-Step Solution
Key Concept: Identify that the thousands digit must be 5 for the given range and use the stars and bars method to find the number of non-negative integer solutions for the sum of the remaining three digits.
<p>21</p>
Correct Answer: A