The perimeter of a rectangle is equal to P = 2(l+w) where l=length and w=width. Here the length is 2/7. This means the width is 3/7. Substitute l=2/7 and w=3/7 into the perimeter equation. Then solve for P.
Let X be a random variable representing the weight of a pack of cookies. P(X < 250) = P(z < (250 - 255)/2.5) = P(z < -5/2.5) = P(z < -2) = 1 - P(z < 2) = 1 - 0.97725 = 0.02275 = 2.3%
Therefore, we conclude that about 2.3% of the packs weighed less than 250 grams.
