Puzzle 221
In each of these sentences, can you replace the missing number.
The number is written as a word (e.g. five, twenty-four, thirty-three), and each sentence is correct after the replacement.
This sentence contains {?} letters, one hyphen, two commas and a full stop.
Interestingly, this sentence contains {?} letters, one hyphen, three commas and the final full stop.
Finally, this sentence contains {?} letters, one hyphen, three commas and one full stop.
Puzzle Copyright © Kevin Stone
workings
hint
answers
print
Share link: https://www.brainbashers.com/puzzle/zzdn
Hint
Start by counting the letters you're given.
Answers
This sentence contains sixty-seven letters, one hyphen, two commas and a full stop.
Interestingly, this sentence contains eighty-nine letters, one hyphen, three commas and the final full stop.
Finally, this sentence contains seventy-nine letters, one hyphen, three commas and one full stop.
Puzzle 222
Alex and Billie have to empty all of the bookshelves in the library, and move the books into storage.
Alex, on her own, can empty the bookshelves in 18 hours.
Billie, on her own, can also empty the bookshelves in 18 hours.
Unfortunately, Drew likes to move the books from storage back onto the bookshelves, and she can refill the bookshelves in 36 hours.
How long will it take the three of them, working at the same time, to empty the bookshelves?
Puzzle Copyright © Kevin Stone
workings
hint
answer
print
Share link: https://www.brainbashers.com/puzzle/ztuw
Hint
How many rooms can Alex clear in 36 hours?
Answer
12 hours.
Reasoning
In 36 hours, Alex could empty 2 lots of bookshelves, Billie could also empty 2 lots of bookshelves, and Drew could refill 1 lot of bookshelves.
So, 2 + 2 – 1 = 3 lots of bookshelves in 36 hours. Which is 12 hours for one lot of bookshelves.
Alternative Reasoning
Alex and Billie can each empty 1/18 of the bookshelves in 1 hour, but Drew will refill 1/36 of the bookshelves in one hour.
So in one hour we have 1/18 + 1/18 – 1/36 = 1/12.
So it would take 12 hours to empty the bookshelves.
Puzzle 223
Can you find a five-digit number that...
...if you place a 9 at the beginning is four times larger than if you place a 9 at the end instead?
Puzzle Copyright © Kevin Stone
workings
hint
answer
print
Share link: https://www.brainbashers.com/puzzle/zcde
Hint
What's a mathematical way to describe placing a 9 at the beginning?
Answer
23,076.
Reasoning
Placing the 9 at the beginning is equivalent to adding 900,000 (for example, 12,345 + 900,000 becomes 912,345).
Placing the 9 at the end is equivalent to multiplying by 10 and adding 9 (for example, 12,345 x 10 + 9 becomes 123,459).
Let's call the unknown number k, and we know that one of these numbers is 4 times the other, so:
k + 900,000 = 4 x (10k + 9)
k + 900,000 = 40k + 36
900,000 – 36 = 40k – k
899,964 = 39k
899,964 ÷ 39 = k
Therefore, k = 23,076.
Double-Checking
923,076 = 4 x 230,769.
Puzzle 224
My first is in camel, and in hamster.
My second is in otter, but not in ferret.
My third is in mustang, but not in horse.
My fourth is in snake, and in asp.
My last is in tiger, and in panther.
What am I?
Puzzle Copyright © Kevin Stone
workings
hint
answer
print
Share link: https://www.brainbashers.com/puzzle/zkha
Hint
The first letter is M.
Answer
Mouse.
Reasoning
My first is in camel, and in hamster = AEM
My second is in otter, but not in ferret = O
My third is in mustang, but not in horse = AGMNTU
My fourth is in snake, and in asp = AS
My last is in tiger, and in panther = ERT
< previous next >
Note: BrainBashers has a Dark Mode option. For BrainBashers, I'd recommend not using your browser's built-in dark mode, or any dark mode extensions (sometimes you can add an exception for a specific website).
