Question 1170808
the half-interval is z(0.975)*sigma/sqrt(n)=1.96*0.8/sqrt(150)
=0.128, which is subtracted from and added to the mean
(5.872, 6.128) units kg

here, the error is 0.1165, and that equals z(0.99)*0.8/sqrt(n)
so 0.1165 *sqrt(n)=2.326*0.8=1.8608
divide both sides by 0.1165 and square the answer, which is 255.12 or 256 apples.
Because a lot of these problems don't round the z-value, which I have, I always go back on the calculator and do a CI check of both n=255 (closest) and n=256 (rounding up, conservative).
n=255 gives the answer exactly.