Comment Comment by colinbeveridge For 13ths, multiply your base number by 77, subtract 1, and concatenate the number that makes it up to 999.So, for 4/13:* multiply 4 by 77 to get 308* subtract 1 to get 307* concatenate 692 to get 3076924/13 is 0.[307692] recurring. (This trick works largely because 77 × 13 = 1001).Seventeenths are trickier, but you can get a decent approximation if you multiply the numerator by 6/100, because 1/17 is 6/102. parent colinbeveridge 3 years ago
So, for 4/13:
* multiply 4 by 77 to get 308
* subtract 1 to get 307
* concatenate 692 to get 307692
4/13 is 0.[307692] recurring. (This trick works largely because 77 × 13 = 1001).
Seventeenths are trickier, but you can get a decent approximation if you multiply the numerator by 6/100, because 1/17 is 6/102.