text: can someone give me some information on the base 5 number system? for example its history, who used it, who invented it,  how it was invented, ect. i know what it is, but i would like to know its backround. base-5 is one of the most primative counting systems.  it was used primarily before the writing of numbers. the signs or words used are hand for 5, two hands for 10, person for 20 (two hands and two feet).   some cultures would count on fingers with 0 being a closed fist and putting a finger up for one, etc, and some cultures would have 0 being an open hand and 1 would be signified by putting a digit down with 5 represented by a closed fist or 5 down.   base 5 was used not as a formalized place value, but rather as a grouping value that combined with other values to a larger grouping value. for example 2 fives (two hands) are 10, 4 fives (two hands and two feet-or person) are 20. 12 fives are 60. each of the groups 10, 20 and 60 were developed into more rigorous numbering systems throughout our globe's cultural history.   the use of 5 as a grouping value is easily understood as the hand has 5 digits. this grouping was used for several hundreds of thousands of years by many cultures around our globe.   in the twentieth century, only the east african luo tribe of kenya and the yoruba of nigeria were still using a base-five system. however, the base-ten (denary or decimal) system has prevailed in most areas and these tribes, like most previously quinary-counting cultures, have converted.  base-5 is still in use in a few places.  for example merchants near mumbai, india will use a base-5 counting system for figuring totals.  this allows them to perform calculations on one hand while serving their customers with the other.  many ancient cultures (roman, chinese, japanese) also used an abacus for counting.  while an abacus is generally used for base-10 calculations, they have a foundation in both base-5 and base-2.  they often have a dividing bar with 5 beads below and 2 beads above for the base-5 and base-2 part of a number.