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Four-large rules
From Countdown
This page details the many different rules to help play four-large numbers rounds on Countdown.
Contents
Simpler rules
- 50 ÷ 25 = 2 or 100 ÷ 50 = 2
- 75 ÷ 25 = 3
- 100 ÷ 25 = 4
- (75 + 50) ÷ 25 = 5
- (100 + 50) ÷ 25 = 6
- (100 + 75) ÷ 25 = 7
- (100 + 75 + 50) ÷ 25 = 9
- 100 + 75 + 50 + 25 = 250
- 50 ÷ 25 × 100 + 75 = 275
- 75 ÷ 25 × 100 + 50 = 350 or (100 + 75) × 50 ÷ 25 = 350
- (100 + 50) × 75 ÷ 25 = 450
- (75 − 50) × 25 = 625 or (100 − 75) × 25 = 625
- (75 − 50) × 25 − 100 = 525
- (100 − 75) × 25 − 50 = 575
- (100 − 75) × 25 + 50 = 675
- (75 − 50) × 25 + 100 = 725
Complex rules
- (75 × 50 ± 100) ÷ 25 = 146/154
- (100 × 50 ± 75) ÷ 25 = 197/203
- (100 × 75 ± 50) ÷ 25 = 298/302
The small numbers can also be added or subtracted before the multiplication to extend this further:
Example 1
25 50 75 100 3 3 → 160
| Answer |
|---|
|
((75 + 3) × 50 + 100) ÷ 25 |
937.5 rule
This rule is based around the calculation:
- 25 × 50 × 75 ÷ 100 = 937.5
As decimals are not allowed in Countdown, small numbers are required to make an integer. This is done in the following ways:
- (25 × 75 ± [odd number]) ÷ (100 ÷ 50)
- (50 × 75 ± [4n + 2]) ÷ (100 ÷ 25) (n ≥ 0)
- (25 × 50 ± [4n + 2]) × 75 ÷ 100 (n ≥ 0. It is required to do the × 75 first in order to keep it an integer)
Example 1
25 50 75 100 3 3 → 939
| Answer |
|---|
|
(25 × 75 + 3) ÷ (100 ÷ 50) |
Example 2
25 50 75 100 2 2 → 937
| Answer |
|---|
|
(50 × 75 − 2) ÷ (100 ÷ 25) |
Example 3
25 50 75 100 6 6 → 942
| Answer |
|---|
|
(25 × 50 + 6) × 75 ÷ 100 |
Very complex rules
- 25 × 100 ÷ (75 + 50) = 20
- 50 × 75 ÷ (100 + 25) = 30
- (100 × 25 + 50) ÷ 75 = 34
- (100 × 50 + 25) ÷ 75 = 67
