Answer
I asked for 9 foot 2 inches (110 inches) and my friend brought me 2 foot 9 inches (33 inches).
Reasoning
I asked my friend to buy me A feet and B inches, which is a total of 12A + B inches.
He accidentally bought me B feet and A inches, which is 12B + A inches.
We know that 12B + A is actually only 30% of what I wanted, so:
12B + A = 0.3 x (12A + B)
Multiply throughout by 10:
120B + 10A = 3 x (12A + B)
120B + 10A = 36A + 3B
117B = 26A
B = 26A ÷ 117
Don't forget that A and B can only be integers, and between 0 and 11.
Since 26 x A has to be at least 117, the lowest possible value for A is 5. We can check the remaining possibilities.
5 x 26 = 130
6 x 26 = 156
7 x 26 = 182
8 x 26 = 208
9 x 26 = 234 (*)
10 x 26 = 260
11 x 26 = 286
The only number wholly divisible by 117 is 234, which means that A = 9, and B = 2.
So, I originally asked for 9 feet 2 inches.
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Puzzle 15
If Malcolm, Laura, John, Alan, Brenda and Kevin like chocolate …
Only people with initials A-M do like chocolate, others do not.
??
Puzzle 16
Hidden in the grid below are eight, 7-letter words. Each word begins with the central P and you can move one letter in any direction to the next letter. All of the letters are used exactly once each. What are the words?
D
I
S
I
S
A
K
M
R
C
N
C
Y
E
A
C
Y
A
H
N
A
H
Y
S
P
I
B
L
I
E
R
O
L
L
S
C
M
P
U
R
A
T
M
U
I
L
A
E
R
Note: this puzzle is not interactive, and the letters cannot be clicked.
