First look at the example 1:

In this part, we mainly call it replacement. See example 1. We need to replace six small cups with two large ones, and then directly add the original number of large cups to the two cups just replaced, * * * three cups, and divide the total juice by three, which is equal to 240 ml.

Better change it to a small one. Replace a large cup with three small cups, add the original amount of small cups, * * * nine small cups, and divide the total juice by 9, which is equal to 80 ml.

It just came out, didn't it?

The second part of this example mainly teaches us to assume that,

We assume that they are all big ships: 10 times 5=50 (people)

Then this number is subtracted from the class size: 50 MINUS 42=8 (people)

The number of people who take more is divided by the number of people who do more in each big boat than in each small boat: 8 divided by (5 minus 3)=4 (only).

Finally, take the total number of ships minus the number of boats: 10 minus 4=6 (only).

So I came out.