Number Properties Puzzle – Challenge 11
This is another great math challenge for those who love critical thinking challenges. This puzzle doesn't require advanced mathematical knowledge, just logical reasoning. Let's see how smart you are!
Challenge:
How many positive integers less than 1000 do not have any 5 as any digits?
A- 700
B- 728
C- 736
D- 770
E- 819
The Absolute Best Book to challenge your Smart Student!
The correct answer is B.
Let’s consider 1 digit, 2 digits, and 3 digits numbers separately:
One digit number: From 9 1-digit numbers, eight numbers don’t have any digit as 5.
Two digits numbers: Put A for \(10^{th}\) place and B for unit place. Then, we have AB as a 2 digits number. We can put 8 digits for A (all digits except 0 and 5) and 9 digits for B (except 5). So, we’ll have 8 × 9 = 72 2-digits numbers that don’t have 5 as any digits.
For three digits numbers, ABC: For A, we can put 8 digits (not 0 or 5), for B, we have 9 digits (not 5) and for C, we have 9 digits (not 5). So, there are 648 three digits numbers that don’t have 5 as any digits. 8 × 9 × 9 = 648
In total: 8 + 72 + 648 = 728
The Absolute Best Books to Ace Algebra
Related to This Article
More math articles
- Pre-Algebra Practice Test Questions
- How to Solve Real-World Puzzles: Division with Decimal Quotients
- Ratio, Proportion and Percentages Puzzle – Challenge 26
- A Comprehensive Collection of FREE PSAT Math Practice Tests
- ISEE Upper-Level Math Formulas
- Number Properties Puzzle – Challenge 15
- 7 Best Headphones for Online Lessons
- Innovative Forecasts: Population Models are Predicting the Future
- 7th Grade Georgia Milestones Assessment System Math Practice Test Questions
- The Ultimate HiSET Math Course (+FREE Worksheets & Tests)
What people say about "Number Properties Puzzle – Challenge 11 - Effortless Math: We Help Students Learn to LOVE Mathematics"?
No one replied yet.