Synonyms for Approximate:

adj.

all (adjective)
approximative, near, rough.
almost accurate, exact (adjective)
close, relative, rough, proximate, near, comparative.
calculational (adjective)
arithmetic, geometric, calculational, judgmental, algebraic, algorithmic, suppositional, rational, proportional, computational, mathematical, valuational, statistical, numerical, Systematical, methodical.
equal (adjective)
rival.
imprecise (adjective)
incorrect, inaccurate, inexact, imprecise.
inexact (adjective)
unscientific, Surmised, Unprecise, imprecise, imperfect, Guessed, estimated, uncertain.
near (adjective)
close together.
representative (adjective)
copy, metaphorical, Rendered, miniature, imitation, Aping, analogous, graphic, portrayed, outline, representative, illustrative, cartoon, facsimile, pastiche, model, replica.
rough (adjective)
fair, approaching, more or less, proximate, estimated, Unprecise, comparative, uncertain, unscientific, Guessed, nearly exact, not quite, nearly perfect, Surmised, imperfect, by means of trial and error, relative, nearly correct, by rule of thumb, coming close.
similar (adjective)
analogous.

n.

amount to, bear/stand comparison (with), have something in common (with something), match, correspond, accord with, coincide, parallel. overtake, reach, come to, touch, fulfill, come, attain, run, enter, push. approximate (noun)
close, gauge, come close, judge, near, inexact, approximative, rough, ballpark, estimate, close together, guess.

v.

calculate (verb)
consider, schedule, figure, account, count, triangulate, presume, rank, gauge, tally, calculate, rate, estimate, infer, plot, conclude, evaluate, add, sum, think, program, value, quantize, suppose, appraise, rationalize, quantify, measure, systematize, determine, enumerate, multiply, scheme, compute, total, deduce, study, reckon, weigh, score, surmise, divide, guess, plan, assess, judge.
come close (verb)
border on, estimate, resemble, touch, verge on, reach, approach.
represent (verb)
portray, silhouette, photograph, render, ape, replicate, imitate, illustrate, duplicate, depict, cast, simulate, represent.
resemble (verb)
mirror, mimic, resemble, look like.
stative (verb)
come close.

Other synonyms:

questionable, amount to, accord with, match, border on, roughly, approximately, more or less. coincide, correspond, parallel. wrong, broadly. touch, put. approach. set. amount
come to, sum, tally.
approach
come close.
comparable
comparative.
Other relevant words:
broadly, estimated, approach, rival, comparative, put, imperfect, uncertain, approaching, come close, border on, challenge, approximative, wrong, verge on, near, place, questionable, parallel, unscientific, not quite, approximately, touch, close, rough, ballpark, relative, set, Surmised, close together, correspond, come, match, Guessed, roughly, Unprecise, proximate, reach.