I started a journey with a certain amount of cash. I spent half of it on lunch, then gave $5 to a friend. After that, I spent half of my remaining money on a book, and was left with $8. How much money did I start with?
$42
Working backwards from the end: $8 doubled is $16. Add the $5 given to the friend to get $21. Double $21 to get the starting amount of $42.
About this riddle
Math riddles hide a calculation inside a short story. Pull out the numbers, work out what is being asked, and watch for a trick such as a unit change.
Difficulty: Medium. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
More math riddles
What single digit, when multiplied by itself, yields a product that ends in that exact same digit, while also being greater than 1?
Noah puts 7 countdown cards in each of 6 boxes. How many countdown cards is that altogether?
If a book has 240 pages and you read 20% of it on Monday, and one-third of the remaining pages on Tuesday, how many unread pages do you have left?
I am a two-digit number. My digits sum up to 10. If you multiply me by 3, the result is a number whose digits are the exact same as mine, just swapped. What number am I?
A wall clock strikes once at 1 o'clock, twice at 2 o'clock, and so on. In addition, it strikes once on every half-hour. How many total strikes does the clock make in a full 24-hour day?
I am a three-digit number. My hundreds digit is the square root of my tens digit, and my units digit is the product of my hundreds and tens digits. None of my digits are identical. What number am I?