How does Snow White need to change her value for mean-dwarf-height after a mix-up?
From the mean weight of five ballet dancers and the mean weight of ten rugby, what is the average weight of all fifteen people?
From the mean of 64 numbers, and the mean of the first 36 of these numbers, can you work out the mean of the last 28 numbers?
Can Emily increase her average test score to more than $80$%? Find out how many more tests she must take to do so.