合計 and 平均: totals and averages
Distinguish totals and arithmetic averages with a simple quantity example.
Adding all the values
合計 (ごうけい) is the sum of several values. 「三日間の合計は六時間です」 says that the total over three days is six hours, not six hours on each day.
「二人の合計」 is the combined value for two people. Read the number of people in the sum rather than treating it as one person's value.
Average per unit
平均 (へいきん) means an average across values. Six hours over three days gives an arithmetic average of two hours per day. 「一日平均二時間です」 does not guarantee exactly two hours on every day.
「平均より高いです」 means higher than the average. It does not mean the highest value; comparison with an average differs from a ranking.
Checking scope and units
「合計金額を確認してください」 asks someone to check the total amount. It differs from asking for an average price. Check what was added and how many items were used as the divisor; equal numbers can have different scopes and units.
「平均を計算しました」 says that an average was calculated. Without the measured quantity and number of values, the exact figure cannot be reconstructed.
For one hour on one day and three hours the next, what are the total and daily average?
Show the answer and why
The total is four hours and the daily average two hours: 「合計四時間、一日平均二時間です」.