Puzzle 1
Starting with any C, using the move of a chess knight, can you find the letters of Christmas in the correct order?
The moves of a knight are:
Puzzle Copyright © Kevin Stone
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Hint
A knight moves in the shape of an L, two squares one way, one square the other.
Answer
Puzzle 3
What value of X makes the following correct:
Puzzle Copyright © Kevin Stone
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Hint
The answer is a whole number less than 10.
Answer
3.
Reasoning
We can multiply throughout by 12,
X X X X
- - - + - = -
X 2 4 12
to give:
12 − 6X + 3X = X
12 − 3X = X
12 = 4X
3 = X
As required.
Double-Checking
3 3 3 3
- - - + - = -
3 2 4 12
1 − 1.5 + 0.75 = 0.25
0.25 = 0.25, which confirms that 3 is correct.
Puzzle 4
During a recent BrainBashers race meeting, the fastest driver managed to complete a lap with an average speed of 150 mph.
They managed to complete the first two fifths of the lap at a speed of 123 mph and the second two fifths of the lap at a speed of 164 mph.
At what speed was the final one fifth of the lap length covered?
The answer is not 176 mph.
Puzzle Copyright © Kevin Stone
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Hint
Adding the speeds won't work.
Answer
205 mph.
Reasoning
If we take the number of miles in a lap to be L miles and use Time = Distance ÷ Speed.
The first 2/5 are covered at 123 mph. Therefore, the time taken was [(2/5) x L] ÷ 123 hours.
The next 2/5 are covered at 164 mph. Therefore, the time taken was [(2/5) x L] ÷ 164 hours.
The last 1/5 is covered at y mph. Therefore, the time taken was [(1/5) x L] ÷ y hours.
The entire trip is covered at an average of 150 mph, and we can conclude that:
2L 2L L L
————— + ————— + ——— = ———
5x123 5x164 5y 150
Rearranging and simplifying gives:
1 1 2 2
——— = —— - ——— - ———
y 30 123 164
That means that y = 1 ÷ (1/30 − 2/123 − 2/164)
Using a calculator gives y = 205.
