Mathematical problems are inverted, what is the mathematical problem solving backwards

Logical comprehension issues.

100*(1+10%)=110 is understood to make a set of mats, and 10% more materials need to be prepared. It is based on the demand for mats.

110*(1-10%)=99 is understood as the material for making 100 sets of mats, and only 90 sets of mats can be made. It is based on the loss of materials.

According to the meaning of demand, the loss rate is considered from the perspective of the material, so the backward formula is correct.

To make 100 sets of mats, the materials that should be prepared are 100 (1-10%) = materials for the mats.

The recommended answer is wrong, and the preparation materials are wrong.

Fan Ina Ena--(2nd floor)

He's right. If the loss rate is 10%, then 100 sets of mats account for (1-10%) of the material to be prepared, that is, 90%. Therefore, the amount used should be 100 90%, that is, 1000 9 = 112, the reason why it is 112 is because in the actual production, only 111 sets of mat materials are definitely not enough.

You can't make a complete mat with poor materials, and the backward push is 1000 9 * (1-10%) = 100

This question should be counted like this:

Set the number of mats to be prepared as x

Then the amount of loss is 10% x =

Calculate x - =100 to get = 100, then x = 1000 9 = 112 (here it is not rounding, it is the balance to an integer).

Therefore, in order to ensure that 100 sets of mats are made, it is necessary to prepare 112 sets of mat materials.

110 sets of mat material 110 * (1-10%) = 99 sets is wrong.

The "attrition rate is 10 percent"To understand correctly.

When working backwards, it is: 110 sets of mat material 110 (1+10%)=100 Note that the inverse operation of multiplication is division,

110 sets of mats according to the 10% loss" means that each set of materials is 10% more, that is, the amount of materials used in each set is "1+10%".

For 100 sets of mats, 100 * (1+10%) = 110 sets of mats must be prepared.

The formula is wrong when counting, it should be: 110 (1+10%)=100 sets.

To make 100 sets of mats, you must prepare 100 (1 10%) = 111 sets of mats.

I think this question is unreasonable, and 1-10% has no basis.

For example, backwards are similar to flashbacks, where the answer is pushed backwards!

Some peaches, the first day to eat all one-seventh, the second day to eat the remaining one-sixth, the next four days to eat the number of the day's one-fifth, one-quarter, one-third and one-half, at this time there are still 12 peaches left, how many peaches are there?

In the end, there are 12 peaches left, which is 1 2 after eating the day before, so there are 12 (2 1) peaches before eating the day before.

12 (2 1) peaches are left over from eating 1 3 the day before.

So that means 12 (2 1) peaches accounted for 2 3 at that time, so before you eat it, it is 12 (2 1) 3 2 peaches.

And so on: there are 12 (2 1) (3 2) (4 3) (5 4) (6 5) (7 6).

The answer is 84.

Forward push: start from the known conditions and prove the conclusion;

Backwards: Start from the verification conclusion and prove the conditions.

Start with the question and roll out the conditions you need to know.