How to calculate 198 times 196 out of 197 in a simple way?

How to calculate 198 times 196 out of 197 in a simple way?

198*196/197
=(197+1)*196/197
=197*196/197+1*196/197
=196+196/197
=196 and 196 / 197

198*198+197*197-198*197-197*196=
Simple operation

=(198-197)*198+(197-196)*197
=198+197=395

Calculation 198 1 / 196 * 1 / 197
There are 96 teachers and apprentices working together. The master can process one by himself with 90 points, and the apprentice can process it with 200 points. The efficiency of the master remains the same, and the apprentice increases by 1 / 3. After a few hours, the master quits and the apprentice does it alone. When the task is finished, the apprentice gains 3200 points more than the master. How many hours of processing?

This kind of problem is very easy to do with the equation. Suppose that the processing time of the master is x points, then the processing time of the apprentice is x + 3200, and the processing time of the apprentice is the same as that of the master, which is x points
The number of master processing is x △ 90, and the number of apprentices processing is x △ 200 × (1-1 / 3)] + 3200 △ 200. According to the total number, the formula is: X △ 90 + X △ 200 × (1-1 / 3)] + 3200 △ 200 = 96