"Approximate" can be either an adjective or a verb: "9.3 is only an approximate value" (adjective); "If you can not find a precision instrument, approximate the value" (verb).

Approximate value, is a value that is not necessarily the right answer but, it is the closest one to it. It means that it isn't exact - but close to the exact value.

Exact value means you do not approximate. So if you answer has a radical in it, you leave the radical and do not approximate it. If it has a fraction such as 1/3, you leave it and do not approximate it as .3 or .33 or even.333333333333333...

It means an approximate value that is calculated rather than an exact value. A value may be estimated because it is quicker or simpler to estimate an approximate value or because there is simply no way to obtain the true value analytically.

Circumference of a circle is pi times diameter therefore C = pi(3.14159265359) * 6 = 18.84955592154 say 18.85 inches (3.14159265359 is the approximate value of pi)