単価 and 総額: the price per unit and the purchase total
Connect the unit price with a stated purchase quantity, keeping one unit’s price separate from the total for the purchase scope.
Which unit the price covers
単価, read たんか, means a price per unit. この部品の単価は二百円です。 gives this part a unit price of two hundred yen.
Check whether the unit is one item or a bundle. Here it is two hundred yen per part, not the total for every part in a bundle.
The amount for the purchase scope
総額, read そうがく, means a total amount. With 三個買います。追加費用はありません。, three parts at two hundred yen each total six hundred yen.
個数に単価を掛けて合計額を求めた。 says that the count was multiplied by the unit price and the total amount was found. Those are the calculation’s two inputs.
Items included in the total
材料費の総額を表の下に記入した。 reports entering total material costs below a table. The stated scope is material costs, without establishing inclusion of other items.
For 総額, check the expense scope as well as the quantity. The no-additional-cost condition in this example is not a rule for every purchase.
If one part costs two hundred yen and three are bought without additional costs, is the total also two hundred yen?
Show the answer and why
No. The total is six hundred yen. Two hundred is the price per part and must be multiplied by three.