Exam questions should have a list of constants for this reason. A couple of questions though: do students have to memorise the exact value; and do they have to do all calculations longhand on paper? If the answer to either is "yes", then this makes sense. If both are "no", then this is bloody stupid.
FWIW, most primary- and early-secondary-school books represent pi as 22/7. It's close enough for that kind of stuff, even if it's not 100% right. So redefining constants to "something convenient for the sums" is not an entirely new concept for school exercises.
Please also bear in mind that all these school exercises start with a zillion caveats like no air resistance/frictionless pulley/non-stretchable string/perfectly elastic collision/perfectly inelastic collision/point mass/infinitely strong beam/etc. In other words you'd better know that it's only ever approximate to the real world anyway!