The mean mass of a squad of 19 hockey players is 82 kg A player of mass 93 kg joins the squad. Work out the mean mass of the squad now.

"Mean" stands for "average", so if you add the mass of all the players together, then divide by the amount of players, you get 82kg. [ (number of players) x (mean mass) = (sum of mass) ] which is ... [ 19 x 82 = 1558 ] To find the new mean, rearrange then update this formula. Since you want to find the mean mass, you want a formula that has "mean mass = ..." , so you divide both sides by the number of players to get... [ (mean mass) = (sum of mass) / (number of players) ] Add the new player's mass, 93, to the "sum of mass", add 1 to the "number of players", then plug these new numbers into the formula to get the new mean. [ (mean mass) = (1558 + 91) / (19 + 1) = 82.45kg ]