Ladybird football team
The ladybird squad members have an average of 12 spots each. How many spots does the pine ladybird have?
Age
14 to 16
Challenge level
Problem
The $6$ member squad for the Ladybirds five-a-side team consists of a $2$-spot ladybird, a $10$-spot, a $14$-spot, an $18$-spot, a $24$-spot and a pine ladybird (as reserve).
The average number of spots for members of the squad is $12$.
How many spots does the pine ladybird have?
Student Solutions
There are six members of the squad, and the average number of spots is $12$.
$\text{Average Spots} = \frac{\text{Total Spots}}{\text{Number of Ladybirds}}$
Therefore
$$\text{Total Spots} = \text{Average Spots} \times \text{Number of Ladybirds} = 12 \times 6 = 72$$
The other ladybirds have a total of $2+10+14+18+24 = 68$ spots.
Therefore the pine ladybird has $72 - 68 = 4$ spots.