The average of a set of values is found by adding up all the values and then dividing by how many there are in the set.
If we want to find the average price of a pencil, that means we should first add up how much money it would cost to buy a bunch of pencils and divide by the number of pencils in the bunch.
Here we have 10 pencils.
6 cost $0.30 each. That is $0.30+$0.30+$0.30+$0.30+$0.30+$0.30 = $1.80. We could have also realized that adding 6 of the same value together is the same as multiplying by 6 – in this case, 6 x $0.30 = $1.80.
The other 4 pencils cost $0.25 each for some reason (maybe they're shorter?). All together, those 4 pencils cost 4 x $0.25 = $1.00.
So when we combine the 6 expensive pencils and 4 cheaper pencils, we get a total cost of $1.80 + $1.00 = $2.80.
So now, to find the average price, we need to divide by how many pencils we bought – 10! That would be $2.80÷10 = $0.28.
The average price of a pencil is therefore $0.28, or 28 cents.