Q1. Arrangements
MCQ · +3 / −1
For which firm(s) can the amounts raised by them be concluded with certainty in each year?
- A) Only Drjbna
- B) Only Czechy
- C) Only Czechy and Drjbna
- D) Only Bzygoo and Czechy and Drjbna
Correct Answer
C) Only Czechy and Drjbna
Step-by-step solution
📌 Core Concept
Each firm's yearly series starts and ends at 1, rises and then falls strictly, and moves by 1 or 2 each year. A firm's amounts are certain only if exactly one series fits its years and total.
🔢 Step-by-Step Solution
1
Drjbna (2011 to 2015, total 10) has the series 1, x, y, z, 1 with x + y + z = 8, where x and z are 2 or 3. If x = 2, then y = 3 forces z = 3, which repeats an amount, so y = 4 and z = 2. If x = 3, then y must be at least 4 and z at most 1, which is impossible. So Drjbna is 1, 2, 4, 2, 1 and is certain.
2
Czechy (starts 2013, total 9) fits 1, 2, 3, 2, 1, which sums to 9. The other short series total 5 (1, 3, 1) or 7 (1, 2, 3, 1 and 1, 3, 2, 1), and 1, 2, 4, 2, 1 totals 10. So Czechy is certain.
3
Bzygoo (2012 to 2015) has the series 1, a, b, 1. Both 1, 2, 3, 1 and 1, 3, 2, 1 obey every rule, so Bzygoo is not certain.
4
Alfloo (eight years, total 21) can be 1, 2, 3, 4, 5, 3, 2, 1 or 1, 2, 3, 5, 4, 3, 2, 1. Both sum to 21, so Alfloo is not certain.
5
Elavalaki (starts 2010, total 13) can be 1, 3, 5, 3, 1 or 1, 2, 4, 3, 2, 1. Both sum to 13, so Elavalaki is not certain.
Only Czechy and Drjbna are fully determined.
Why Not the Others
A leaves out Czechy, which is also certain.
B leaves out Drjbna, which is also certain.
D wrongly includes Bzygoo, which has two valid series.
Correct Answer: C