Number Detective
You need to
be a detective to uncover the value of my secret number. Follow the clues below. You must use the clues in the order given.
a) What is
my number?
b) What is
the least number of clues you need to use to be absolutely certain of the value
of my number?
The clues:
1. I am a
three digit number.
2. I am an
odd number.
3. I am
divisible by 5.
4. Each of
my digits is different.
5. My digits
add up to 8.
6. The tens
digit is smaller than the hundreds digit.
7. I am less
than 300.
8. I have
only one even digit.
Solution:
Work through each clue one by one.
1. _ _ _
2. Must have 1, 3, 5, 7 or 9 in the units place.
3. Must end in 5 or 0, so _ _ 5.
4. The hundreds and tens place cannot be 5.
5. 5 + ? = 8 so the hundreds and tens digit must add to 3, so the number could be 215,125 or 305.
6. It could be 215 or 305.
7. It can only be 215.
Seven clues are needed.
Work through each clue one by one.
1. _ _ _
2. Must have 1, 3, 5, 7 or 9 in the units place.
3. Must end in 5 or 0, so _ _ 5.
4. The hundreds and tens place cannot be 5.
5. 5 + ? = 8 so the hundreds and tens digit must add to 3, so the number could be 215,125 or 305.
6. It could be 215 or 305.
7. It can only be 215.
Seven clues are needed.
