95.--THE FOUR SEVENS.

From Amusements in Mathematics by Henry Ernest Dudeney.

The way to write four sevens with simple arithmetical signs so that they represent 100 is as follows:--

7 7 -- × -- = 100. .7 .7

Of course the fraction, 7 over decimal 7, equals 7 divided by 7/10, which is the same as 70 divided by 7, or 10. Then 10 multiplied by 10 is 100, and there you are! It will be seen that this solution applies equally to any number whatever that you may substitute for 7.

Read and discuss in amphi

A place to think
Built for depth, not dopamine. Come thinkwith us
explore the betaDither Right Arrow
FIND US
amphi.
95.--THE FOUR SEVENS.: Amusements in Mathematics by Henry Ernest Dudeney | amphi