What fraction is halfway between 1/3 and 1/5?

1 Answer
George C.
Sep 11, 2015

#4/15#

Explanation:

A trick question: The obvious, but wrong answer is #1/4#.

Actually #1/4# is called the harmonic mean of #1/3# and #1/5# - being the reciprocal of the average of the reciprocals.

To find the number halfway between #a# and #b#, calculate #1/2(a+b)# ...

#1/2(1/3+1/5) = 1/2(5/15+3/15) = 1/2(8/15) = 4/15#

Note that to add the fractions #1/3# and #1/5# we first give them a common denominator #15# by multiplying them by #5/5# and #3/3# respectively. Once we have a common denominator, then we can just add the numerators.

Related questions
See all questions in Properties of Rational Numbers
Impact of this question
26342 views around the world
You can reuse this answer
Creative Commons License