Seven parcels have a mean mass of 6 kilograms. One parcel is taken away and the remaining six parcels have a mean mass of 5 kilograms. What was the mass of the parcel that was taken away? Enter the number of kilograms.

Բացատրություն

Seven parcels averaging 6 kilograms total 42 kilograms, and the six that remain average 5 kilograms and so total 30 kilograms, which makes the parcel removed 42 - 30 = 12 kilograms. The mean falling by 1 kilogram does not make the removed parcel 1 kilogram, since a mean drops only when something well above it leaves the set.