Hint
It will take a while to check 1 x 7, 2 x 7, 3 x 7. What do we know about the answer?
Answer
63,492 x 7 = 444,444
Reasoning
We can work backwards, as we know that the number multiplied by 7 has only 4's. We can try the following:
4 ÷ 7 ≈ 0.57 x
44 ÷ 7 ≈ 6.29 x
444 ÷ 7 ≈ 63.43 x
4,444 ÷ 7 ≈ 634.86 x
44,444 ÷ 7 ≈ 6,349.14 x
444,444 ÷ 7 = 63,492
?
Puzzle 2
Look at the following sentence once, and once only. How many times can you find the letter F?
Furry foxes of far origin often come of age far before scientific study forecasts.
Hidden in the grid below are eight, 7-letter words. Each word begins with the central R 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?
T
A
E
R
O
B
O
E
T
G
S
T
N
W
R
N
E
E
A
I
E
I
N
U
R
E
F
R
N
B
U
O
E
E
E
B
S
E
A
E
V
E
I
D
H
T
S
G
N
Note: this puzzle is not interactive, and the letters cannot be clicked.
Hint
How many students study chemistry and physics, but not biology?
Answer
500 students.
Reasoning
The answer is more easily seen if three intersecting circles are drawn, and the numbers inside each section are worked out.
We know that 73 students study all three disciplines, which allows us to work out the numbers.
97 students study chemistry and physics, so 97 − 73 = 24 study just chemistry and physics.
138 students study physics and biology, so 138 − 73 = 65 study just physics and biology.
152 students study chemistry and biology, so 152 − 73 = 79 study just chemistry and biology.
280 students study chemistry, so 280 − 73 − 24 − 79 = 104 study just chemistry.
254 students study physics, so 254 − 73 − 24 − 65 = 92 study just physics.
280 students study biology, 280 − 73 − 65 − 79 = 63 study just biology.
For a total of: 104 + 92 + 63 + 24 + 65 + 79 + 73 = 500 students.
