... ;echo "and the average of these grades is: " . round($avgGrades,2) ; The sum of the provided grades is: 564 The average of these grades is: 80.57This code also uses the round function ... code, you can reference the elements of an array by their keys, surrounded bysquare brackets. If we want to take the value of the third element of the array the contents being the number 3 in this ... number) to the end of the array, but because we donot provide a key, when we var_dump the array we get output showing that the lastelement in the array has the key of 0, which is the next numerical...