Category Archives: brain teaser

May 2018 Brain Puzzler Solution

Q: Two coins are flipped and you cannot see the outcome but are told that at least one is a head.  What is the probability that the other coin also landed on heads?
A: 1/3
This is a classic probability question.  Once you know that one coin is a head, there are 3 possible outcomes for the two coins with at least one head.
Since you know that one is a heads, and there are 3 possible outcomes, the probability is 1/3.

October 2017 Brain Puzzler Solution

Q:  Write down all the integers from 1 through 60 to form the number
Now delete 100 digits from this number.
Without rearranging the digits, what is the largest number possible?

A:  Writing down all integers from 1 through 60 gives you a number 111 digits long:
9 numbers at 1 digit apiece: 9 digits
51 numbers at 2 digits apiece: 102 digits
Total: 111 digits.

So deleting 100 digits leaves us with 11 digits.  It’s be best to have as many 9’s as we can as far to the left as we can. But there’s only 6 of those, and one of them is already in the hundreds place before we do any deleting.
If we’re not allowed to rearrange the digits, the largest number is:
99 999 785 960.

October 2016 Brain Teaser Solution

Q:       MAD + AS + A = BULL
Each letter stands for a number 0 -9 but not all digits will be used.
If D = 3 and L = 7, find the value of the other letters

983 + 86 + 8 = 1077
writing it vertically helps a lot
The B has to be a 1 as the total would be over 1000 and the M has to be a 9 as we are only adding a two digit and 1 digit number and getting over 1000


the last column must be adding up to 17 rather than 7 (otherwise S + A would be 4 and would be 1 and 3 but 3 is already used)
so S + A = 14 and since there will be a carry the next column over A + A + 1 will equal 17
so A = 8 and therefore A = 6