The easy way to ielts writing academic Module

As shown in the above examples, “percentage,” “proportion,”
and “rate” are accompanied by the definite article “the” and
the preposition “of” in most cases. However, if an adjective
defines these words, “the” changes to “a/an” accordingly. This
feature is quite similar to what was described previously
regarding “the number of” and “the amount of.”
For example
The percentage 
of female employees vs. 
a high percentage 
of female
employees
The proportion 
of imported goods vs. 
an enormous proportion 
of
imported goods
Approximation
It is crucial to use approximation vocabulary if the numbers and figures we
describe are not exact. For instance, if the figure is “39%”, we can round it up
using the vocabulary of approximation and describe it as “almost 40%”, or in
case the figure on the graph or chart is hard to read precisely, and it is
somewhat between 30% and 40%, we can use the vocabulary of
approximation and refer to it as “roughly 35%”. The following sentences
show how to make use of the vocabulary of approximation:
For example
Approximately 10% of the population is over 75 years old.
Almost all students attended the session.
Around 40% of students passed the test.
About a quarter of the females in the program received a promotion.
Roughly half of the male candidates received approval.
Nearly 30% of people voted for the election.
Just below 20% of citizens were eligible for the application.
Just above 15% of students were qualified to pass.