Find the total 4-digit figures can be made using the numbers 2, 4, 6, 3, 5, 7,…
2025
Find the total 4-digit figures can be made using the numbers 2, 4, 6, 3, 5, 7, 9 and 8 without repetition, that are completely dividable by 5?
Answer: C. 210 — Key idea: a number is divisible by 5 only if its last digit is 0 or 5. Only 5 is available from the given digits, so the units digit must be 5. Fix the units…
- A.
910
- B.
250
- C.
210
- D.
510
Attempted by 34 students.
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Correct answer: C
Key idea: a number is divisible by 5 only if its last digit is 0 or 5. Only 5 is available from the given digits, so the units digit must be 5.
Fix the units (ones) digit as 5.
Choose the thousands (first) digit from the remaining digits {2,4,6,3,7,9,8}: 7 choices.
Choose the hundreds (second) digit from the remaining digits after those two are used: 6 choices.
Choose the tens (third) digit from the remaining digits: 5 choices.
Total number of 4-digit numbers = 7 × 6 × 5 = 210.
Answer: 210