4) Use the formula for the area of a trapezium. Consider what the possible range of the various numbers might be, given their reported value, and how changes in value affect the area.
The area will be in the interval [445, 455) cm^2. The length of the shorter parallel side will be in the interval [17.5, 18.5) cm. The length of the longer parallel side will be in the interval [21.5, 22.5) cm. The area is given by .. A = (b1 +b2)/2*h .. h = 2A/(b1 +b2)
h will get smaller when A gets smaller, so we want to do our calculation with the minimum value of A, 445 cm^2. h will get smaller when b1 and b2 get larger, so we want to do our calculation with the maximum values of those numbers, 18.5 and 22.5 cm.
The minimum value of h will be .. h = 2*(445 cm^2)/(18.5 cm +22.5 cm) = 21.7 cm
5. In the worst case, the lorry is limited to a load of .. (14.5 -2.35)/(.255) = 47 . . . . crates
This is computed as the minimum safe additional load divided by the maximum mass per crate.
