Fiendish Maths Riddles April 2017

27th March 2017

We hope you enjoy these mathematically themed riddles, share them with your friends and family to make yourself look like a real brainbox!

How can you make the following true by changing a single line? 5+5+5=550

Add a line to make the first + a 4 545+5=550


When was the last year that reads the same upside down?



A girl was ten on her last birthday, and will be twelve on her next birthday. How is this possible?

Today is her eleventh birthday


You want to hire a temporary employee for one month. You offer him reasonable wages, but the employee suggests an alternative. For the first day of work, he will be paid a penny. For the second day, two pennies. For the third day, four pennies. The salary for each subsequent day will be double the previous day's, until the one month term is over. Ignoring the legalities of such a situation, would it be a good idea to accept the potential employee's proposal?

Not at all. He would earn $5,368,709.12 on the thirtieth day alone.


If you go to the movies and you're paying, is it cheaper to take one friend to the movies twice, or two friends to the movies at the same time?

It's cheaper to take two friends at the same time. In this case, you would only be buying three tickets, whereas if you take the same friend twice you are buying four tickets.


Of all the numbers whose literal representations in capital letters consists only of straight line segments (for example, FIVE), only one number has a value equal to the number of segments used to write it. Which number has this property?



When I take five and add six, I get eleven, but when I take six and add seven, I get one. What am I?

A clock


If two hours ago, it was as long after one o'clock in the afternoon as it was before one o'clock in the morning, what time would it be now?