What number am I? 1.
I am the 11th odd number.
2.
I am the 200th odd number.
3.
I am the 7th triangular number.
4.
I am the sum of the 5th prime number and the 5th Fibonacci number.
5.
I am the sum of the factors of 48.
6.
I am a square number.
I am a multiple of 5.
I have three digits.
The sum of my digits is a prime number.
7.
I am a palindrome.
My digits are all square numbers
My four digits sum to 10.
My first digit is larger than my second.
8.
I am a cube number.
I am a square number.
I am an odd number.
My middle digit is prime.
I have fewer than six digits.
9.
I am a Fibonacci number.
I am a prime number.
My four digits are all odd.
10.
I am an even triangular number.
I have three digits.
I am a perfect number.
The product of my digits is 216.
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What number am I? Answers
The following answers contain some suggested hints which may help students get
started or narrow down the possible solutions.
1.
11th odd number = 21
2.
200th odd number = 399
3.
7th triangular number = 28
4.
5th prime number + 5th Fibonacci number = 11 + 5 = 16
5.
Sum of factors of 48 = 1 + 2 + 3 + 4 + 6 + 8 + 12 + 16 + 24 + 48 = 124
6.
I am 625.
7.
I am 4114.
8.
I am 729.
Hint: There are less cube numbers than square numbers with fewer than
six digits. Have a look at those first!
9.
I am 1597.
Hint: Try listing out the four digit numbers in the Fibonacci sequence;
there are fewer than you’d think!
10.
I am 496.
Hint: All even perfect numbers end in 6 or 8.
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