This is more maths than a riddle, but it will still fuck your head up!
You saw a shirt for £97.
You didn't have the cash, so you borrowed £50 from your mom and £50 from your dad = £100.
You bought the shirt and had £3 change.
You gave your dad £1 and your mom £1 and kept the other £1 for yourself.
Now you owe your mom £49 and your dad £49.
49+49 = 98 + your £1 = 99.
Where is the missing £1?
Bookmarks