Math problems, hurry up, I ll give 10 more points when it comes out in 20 minutes

It adds up to how much this is your turnover of 1620

Profit 1620-1500=120

Profited, according to the current selling method of a total of 1,620 yuan, excluding the purchase of 1,500 yuan, now the profit is 120 yuan. But there is little profit. It's a small business. If you include booth fees and so on, it seems to be a loss.

3x500=1500 yuan (500-200-100=200 pairs.)

Yuan 540 + 648 + 432 = 1620 yuan 1620-1500 = 120 yuan.

Earned, earned 120 yuan.

The children's clothing store buys 500 pairs of children's shoes, and the purchase price of each pair is 3 yuan 3 * 500 = 1500 yuan retail price. Sell 100 pairs.

The retail price is 60% off** 200 pairs.

300 pairs were sold, and there were 200 pairs.

Sold out at 4% off retail price.

Yuan. 540 + 640 + 432 = 1612 turnover.

1612-1500=112 yuan.

Income 112 yuan.

100*(Yuan is greater than 0.)

So it made a profit, a profit of 120 yuan.

Question 2: You won't be able to ??? Scientific notation.

If x acres of land are planted with spinach, then (25-x) acres of land are planted with tomatoes according to the title.

1700x+1800(25-x)=4400017x+18(25-x)=440

17x+450-18x=440

x=1025-x=15

That is, 10 acres of spinach and 15 acres of tomatoes were planted.

So a total of profits.

63,000 yuan.

Tomato x, spinach y

x+y=25

1800x+1700y=44000

The solution is x=15 and y=10

Profit s=2600*15+2400*10=63000 yuan.

Let the total capacity of the bathtub be v, then the total time of method 1 is .

t1=(v 2a)+(v 2b)=(a+b)v (2ab) Let the total time of method 2 be t2, then.

at2/2+bt2/2=v

t2=v [(a 2)+(b 2)]=2v (a+b) t1 t2=(a+b) (4ab)=(a +2ab+b) (4ab) 1 (by mean inequality a +b 2ab).

t1 t2 So the second way is more time-saving.

You have a problem with this question, because there is no way to put the water according to method 2.

Reason: The first half of the time to put hot water, the second half of the time to cold water, how to determine the first half of the second half of the time, do you know how long it takes to release water before releasing water, and the speed of the faucet in 2 is different, so there is no way to determine the first half of the time and the second half of the time.

The tank can be filled with water x

Scheme 1: x 2a + x 2b

Solution 2: x 2(a+b)a+x 2(a+b)b, solution 1 saves time.

I have to use my brain to talk about this problem, let me tell you my opinion, just use the extreme method, first of all, if a=b, then the time used by the two methods is the same, if b>a, then let a=0, then the time used for method 1 is infinite, and the time used for method 2 is limited.

If a>b then let b=0 then the time taken by method 1 is infinite, and the time used by method 2 is limited.

To sum up, method 1 will not be faster than method 2, so choose method 2.

Let the total amount of water be 1, then:

Way 1. The time taken is:

1/2a + 1/2b=(a+b)/2ab=(a+b)^2 / 2ab(a+b) （1）

Way two. A * H2 + B * H2 = 1, so H = 1 (A 2 + B 2) = 2 (A + B) = 4ab 2 Ab (A + B) (2).

(1)-(2) again;

a+b) 2 - 4ab] 2ab(a+b)=(a 2+2ab+b 2-4ab) 2ab(a+b)=(a-b) 2 2ab(a+b) (3) and (3) must be greater than or equal to 0;

So the first way is more time-saving.

What is the purpose of this topic? What is the desired effect? Like, whether it's filled with water, or whatever. There are no restrictions on the title. Not rigorous.

Both sides are minus 2 3 = 6

So it's actually (a-6) (b-6) square centimeters.

Cm.

Cm.