It costs 24.6 yuan to buy three science books and five story books, and 5.8 yuan to buy one science book and one story book How much is a science book and a story book?

It costs 24.6 yuan to buy three science books and five story books, and 5.8 yuan to buy one science book and one story book How much is a science book and a story book?

Suppose that the science and technology book is X Yuan and the story book is y yuan, then there are: 1:3x + 5Y = 24.6, 2: x + y = 5.8
Through formula 2 * 3 and formula 1-2, we get y = 3.6, x = 2.2
Therefore, a science book costs 2.2 yuan and a story book costs 3.6 yuan

It costs 24.6 yuan to buy 3 science and technology books and 5 story books, and 5.8 yuan to buy 1 science and technology book and 1 story book?

It costs 20 yuan to buy a story book and a technology book, and 72 yuan to buy three story books and four technology books
It costs 20 yuan to buy a story book and a science and technology book, and 72 yuan to buy three story books and four science and technology books. How much is a story book? How much is a science and technology book?

Analysis: if you multiply the amount of money used for a story book and a science and technology book by 20 times 3, you can get that three story books and three science and technology books share 60 yuan. If you use 72-60 yuan, you can get the amount of money for a science and technology book, and you can also get the amount of money for a story book
20 × 3 = 60 yuan
72-60 = 12 yuan
20-12 = 8 yuan
A: 8 yuan for a story book and 12 yuan for a science and technology book

If there is a real number x such that cos α = x / 2 + 1 / 2x holds, then the set of values of real number x is?

I know it can be calculated by taking the derivative on both sides, but I forget how cos leads (> ﹏)

The difference between a and B is 80, 1 / 2 of a is equal to 2 / 3 of B, what are the two numbers?

Number A: number b = 2 / 3:1 / 2 = 4:3
Number of a = 80 ÷ (4-3) × 4 = 320
B = 320-80 = 240

What is the integer to the power of 1-200 of 2
It's an integer

From 0 to 200 power of 2 0:11:22:43:84:165:326:647:1288:2569:51210:1024

On the road, a truck is driving at the speed of 70 km / h, and a car is catching up 30 km away from him. It's still two hours away
You can catch up with the truck within 10 kilometers. Please find the speed of the car

Let X be the speed of the car
2(x-70)=30-10
2x-140=20
2x=140+20
2x=160
x=80
If other problems are added,

The shape of the triangle can be judged by ∠ a = 2 ∠ B = 2 ∠ C in △ ABC

In △ ABC
∵∠A=2∠B=2∠C
∴∠B=∠C=∠A/2
And ∵ a + B + C = 180 degree
∴∠A+∠A/2+∠A/2=180°
I.e. 2 ∠ a = 180 degree
∠A=90°
The ABC is an isosceles right triangle
The team wdxf4444 will answer for you!

The distance ratio of the two vehicles is 5:4 when they meet. After meeting, the freight car is 18 kilometers faster than the passenger car per hour,
As a result, the two cars arrived at the other side's departure station at the same time. It is known that the freight car has been running for 10 hours. How many kilometers is the distance between a and B?

After the meeting, the distance ratio of freight and passenger cars is 5:4
After meeting, the speed of the freight car is 5 / 4 of that of the passenger car
After meeting, the speed of the bus is 18 (5 / 4-1) = 72 km / h
The distance between a and B is 72x10 = 720km
A: the distance between a and B is 720 kilometers
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How to do this geometry problem may be decided by projection
The triangle ABC angle BAC = 90, and AC is greater than AB, ad is the height on the side of BC, and M is the midpoint of BC, which means that the square of AC minus the square of AB = 2Md times BC

AC^2-AB^2
=CD*CB-BD*BC
=(CD-BD)*BC
=(CM+MD-BD)*BC
=(BM+MD-BD)*BC
=2MD*BC