A merchant buys a clock for $60, sells it for $70, buys it back for $80, and finally sells it for $90. What is the merchant's total profit?
$20
Track the cash flow: First transaction (-$60 + $70 = +$10). Second transaction (-$80 + $90 = +$10). Total profit is $10 + $10 = $20.
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: Hard. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
More math riddles
A cyclist pedals up a mountain road at a steady 10 miles per hour, then turns directly around and descends along the identical route at 30 miles per hour. What was the cyclist's average speed for the full round trip?
A clock strikes 6 times in 5 seconds. How many seconds will it take for the same clock to strike 12 times?
If 3 chickens lay 3 eggs in 3 days, how many days does it take for 12 chickens to lay 12 eggs?
A lily pad doubles in size every single day. If it completely covers a pond in 30 days, on which day was the pond exactly half covered?
A box contains blue, red, and green socks. If you close your eyes, what is the minimum number of socks you must pull out to guarantee you have at least one matching pair?
Stand me up and I am a digit of great power, but lay me down on my side and I become endless. Take away my top half and I become a zero. What number am I?