Puzzle 685
In my money box, I found $36.80 made up of equal numbers of quarters, dimes, and nickels.
How many of each coin did I find?
Puzzle Copyright © Kevin Stone
workings
hint
answer
print
Share link: https://www.brainbashers.com/puzzle/zryo
Hint
Remember that a quarter is 25c, a dime is 10c and a nickel is 5c.
Answer
92 of each coin.
Reasoning
There are an equal number of quarters, dimes and nickels, so we know that the answer must be a multiple of:
25c + 10c + 5c = 40c
and:
3680c ÷ 40c = 92 coins.
Puzzle 686
What number comes next in the sequence:
11 13 17 31 37 71 73 79 97 {?}
Puzzle Copyright © Kevin Stone
workings
hint
answer
print
Share link: https://www.brainbashers.com/puzzle/zuke
Hint
A very tricky puzzle involving prime numbers.
Answer
101.
These are prime numbers, which, when reversed, are also prime.
Puzzle 687
How much soil is there …
… in a circular hole 2 metres deep and 1 metre across?
workings
hint
answer
print
Share link: https://www.brainbashers.com/puzzle/zpof
Hint
How much soil is in any hole?
Puzzle 688
What is the smallest positive integer which, when multiplied by 7, gives an answer consisting of only 4's?
Puzzle Copyright © Kevin Stone
workings
hint
answer
print
Share link: https://www.brainbashers.com/puzzle/zwgz
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
< 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).
