Puzzle 213
What is the 10th prime number?
2, 3, 5, 7, …
workings
hint
answer
print
www.brainbashers.com
/puzzle/zhgx
share
Hint
The first nine prime numbers are: 2, 3, 5, 7, 11, 13, 17, 19, 23.
Answer
29.
The first ten prime numbers are: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29.
Puzzle 214
How many squares, of any size, are on a board divided up into 6 squares by 6 squares?
workings
hint
answer
print
www.brainbashers.com
/puzzle/ztki
share
Hint
How many 1 x 1 squares are there?
Answer
91 squares.
Reasoning
Squares of size:
1 x 1 = 36
2 x 2 = 25
3 x 3 = 16
4 x 4 = 9
5 x 5 = 4
6 x 6 = 1
Total = 36 + 25 + 16 + 9 + 4 + 1 = 91.
Puzzle 215
hwayetritipzl
omnltesnhsuze
Puzzle Copyright © Kevin Stone
workings
hint
answer
print
www.brainbashers.com
/puzzle/zfzk
share
Hint
The puzzle contains the question.
Answer
26.
Reasoning
The puzzle reads 'how many letters in this puzzle'.
The puzzle's letters alternate between the top and bottom lines.
Puzzle 216
Can you find three consecutive prime numbers …
… that equal 409,457 when multiplied together?
Puzzle Copyright © Kevin Stone
workings
hint
answer
print
www.brainbashers.com
/puzzle/zahu
share
Hint
The cube root of the given number is a good starting point.
Answer
71, 73, 79.
Reasoning
The cube root of 409,457 is around 74.
The closest consecutive prime numbers to 74 are: 61, 67, 71, 73, 79, 83, 89, 97.
Using a calculator, it is quickly seen that the answer can only be found using 71, 73 and 79.
