Fill in the missing numbers with the digits 1 to 9. A diamond shape in the middle means that the four numbers around it add to 20.
Each uses a different way to add to 20, if there is already 1 + 3 + 7 + 9, then there will not be another using the digits 1, 3, 7 and 9 (in any order).
The same digit isn't allowed to touch, even diagonally.
At the recent BrainBashers downhill mountain bike race, four entrants entered the challenging slalom event.
Alex finished in first position. The entrant wearing number #2 wore red, but Drew didn't wear yellow. The person in last place wore blue, and Stevie wore number #1. Glen beat Stevie, and the person who finished in second wore number #3. The entrant in yellow beat the entrant in green. Only one of the entrants wore the same number as their final position.
Can you determine who finished where, the number, and colour they each wore?
Hint
Start by looking at where Alex finished, and where the person who wore #3 finished, and then use clue (6).
Answer Pos Name Wore Colour
1 Alex #2 red
2 Glen #3 yellow
3 Stevie #1 green
4 Drew #4 blue
Reasoning
The four colours were: blue, green, red, yellow.
The four contestants were: Alex, Drew, Glen, Stevie.
By (1), Alex was first.
1 Alex
2
3
4
By (4), the person who was second wore number #3.
1 Alex
2 #3
3
4
Looking at (6):
- first place (Alex) can't have worn #1, because, by (3), Stevie wore #1
- second place wore #3
- third place can't have worn #3, because it was worn by second place
- fourth place is the only entrant who could have worn the same number as their final position
Therefore, Stevie finished in third, and Alex wore #2.
1 Alex #2
2 #3
3 Stevie #1
4 #4
By (2), Alex wore red. By (3), the person wearing blue was last.
1 Alex #2 red
2 #3
3 Stevie #1
4 #4 blue
By (5), yellow beat green.
1 Alex #2 red
2 #3 yellow
3 Stevie #1 green
4 #4 blue
By (4), Glen beat Stevie.
1 Alex #2 red
2 Glen #3 yellow
3 Stevie #1 green
4 #4 blue
Leaving Drew in last place.
1 Alex #2 red
2 Glen #3 yellow
3 Stevie #1 green
4 Drew #4 blue
??
Puzzle 199
What is the minimum number of queens required on a chessboard such that all squares are attacked?
Hint
We'll assume that we can actually fold it this many times.
Answer
Very thick indeed! The paper doubles in thickness with each fold. If we could fold it 50 times, it would be around 70 million miles thick!
1 fold would be 0.1 + 0.1 = 0.1 x 2 ^ 1 = 0.2 mm
2 folds would be 0.1 + 0.1 + 0.1 + 0.1 = 0.1 x 2 ^ 2 = 0.4 mm
.
.
.
.
10 folds would be 0.1 x 2 ^ 10 = 102.4 mm
.
.
.
50 folds would be 0.1 x 2 ^ 50 = 112,589,990,684,262.4 mm = 112,589,990.7 km (around 70 million miles).
