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Tonight math
Teacher Jay's answer, I hope to bring you help ~ ~:)

1, travel problem: distance = speed × time,

In the clock problem, a circle is 60 minutes, the minute hand speed is 1 min/min, and the hour hand speed is (112) min/min.

In the pursuit problem, the distance between them is = (speed A- speed B) × time.

2. Engineering problems: workload = working efficiency × working time

If the workload does not give a specific value, the unit is 1. Work efficiency is expressed by (1/ completion time).

3, concentration problem:

Solute = solution × concentration

Solution = solute+solvent

Constant Solute Relation Equation before and after Common Configuration

4. Number problem: For example, abc with three digits can be expressed as (100a+ 10b+c), and then the problem can be solved by an equation.

5, commodity profit problem:

Profit = selling price-buying price

Selling price = list price × discount = purchase price ×( 1+ profit rate)

Profit rate = profit/purchase price

6. Bank storage problems:

Interest rate = interest/principal

Interest = principal × annual interest rate× year

Sum of principal and interest = principal+interest = principal ×( 1+ annual interest rate× year)

7, navigation problems:

Downstream speed = ship speed+current speed

Countercurrent speed = ship speed-current speed

This topic is a typical engineering problem, please read it carefully.

1, if A works alone for 30 hours, then A's work efficiency is (1/30).

The cooperation between Party A and Party B is completed within 24 hours, so the sum of Party A's efficiency is (1/24). At this time, it can be calculated that Party B's work efficiency is (1/24)-(1/30) =1120, that is, Party B completes it alone.

Solution: Let the remaining B take X hours to complete, and there is an equation.

[( 1/24)-( 1/30)]* x = 1-[( 1/30)* 10]

The solution, x=80,

A: It takes 80 hours to complete, and it takes 1 hour to complete all (1120).

2. Set the rest of the cooperation, including

( 1/24)* x = 1-[( 1/30)* 10]

x= 16

A: Cooperation, 16 hours.

3. A first worked 10 hour and finished (1/30)* 10.

B did it for another five hours, and finished it (1120) * 5.

Assuming that the cooperation is completed within x hours, use (1/24) x.

There is also an equation for all work units that add up to 1.

( 1/30)* 10+( 1/ 120)* 5+( 1/24)x = 1

x= 15,

A: It takes 15 hours to complete!

Do you understand ~ ~:) Do more problems, master various types, and use their relationships to make equations, and there will be no problem. Come on, you can do it! ! !