Puzzle 109
Starting in the bottom left corner and moving either up or right, how many ways are there to get to the top right corner and make a total of 10?
Note: this puzzle is not interactive, and the numbers cannot be clicked.
Puzzle Copyright © Kevin Stone
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Hint
You can only go up, or right.
Answer
6.
With U = Up, and R = Right, you can move in the following ways:
UURR
URUR
URRU
RUUR
RURU
RRUU
Puzzle 110
In each of these 5 words, can you change the underlined letter to produce a new word?
The new letters, in order, spell a fruit.
D ate
nU t
L ime
pE ach
P ear
Puzzle Copyright © Kevin Stone
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Hint
The last letter is N.
Answer
L ate
nE t
M ime
pO ach
N ear
The new letters spell LEMON.
Puzzle 111
Which is larger:
millimetres in a mile
sixteenths of an inch in 2 kilometres
Puzzle Copyright © Kevin Stone
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Answer
Millimetres in a mile.
Reasoning
One inch = 25.4 mm.
So:
1 mile = 1760 yards = 1760 x 3 feet = 1760 x 3 x 12 inches = 1760 x 3 x 12 x 25.4 millimetres = 1,609,344 mm in 1 mile.
And:
2 kilometres = 2000 metres = 2000 x 100 centimetre = 2000 x 100 x 10 millimetres = 2000 x 100 x 10 ÷ 25.4 inches = 2000 x 100 x 10 ÷ 25.4 x 16 = sixteenths of an inch ≈ 1,259,843 sixteenths of an inch in 2 kilometres.
Puzzle 112
Can you find three consecutive odd numbers that …
… total 7,644,585 when multiplied together?
Puzzle Copyright © Kevin Stone
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Hint
Try starting with the cube root of the number.
Answer
195 x 197 x 199.
Reasoning
Since we're after three numbers that multiply together, a good place to start is the cube root of 7,644,585, which is roughly 196.99.
Let's try dividing by the closest odd number to 196.99:
7644585 ÷ 197 = 38805
We're now after whole divisors of 38,805, so trying either odd number either side of 197 might work.
Trying either 195 or 199 gives the answer.
Double-Checking
195 x 197 x 199 = 7,644,585
Note
Trying the closest odd number to the cube root always works, and the other two numbers are the odd numbers either side.
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