A primary school donated 6800 yuan to five classes of grade six in the activity of "giving love - donating money to Wenchuan disaster area". Among them, class one donated 1500 yuan, and class two donated less than class one The donation is 200 yuan. The donation of class three is 20% of the total amount of the grade. The ratio of donation of class four to class five is 19:21?

A primary school donated 6800 yuan to five classes of grade six in the activity of "giving love - donating money to Wenchuan disaster area". Among them, class one donated 1500 yuan, and class two donated less than class one The donation is 200 yuan. The donation of class three is 20% of the total amount of the grade. The ratio of donation of class four to class five is 19:21?

Is it true that the five classes in Grade 6 donated 6800 yuan in total, among which class 1 donated 1500 yuan, and class 2 donated 200 yuan less than Class 1,
Donation for class three: 6800 × 20% = 1360 yuan
Total donation of class 4 and 5: 6800-1500 - (1500-200) - 1360 = 2640 yuan
Donation for class 4: 2640 × 19 ÷ (19 + 21) = 1254 yuan

Urgent! Write a letter to the children in Wenchuan earthquake~

The story of parents saving their children in Wenchuan earthquake

As shown in the figure, fold the rectangular paper ABCD so that vertex B and vertex D coincide, and the crease is EF. If AB = √ 3, ad = 3, then the perimeter of △ DEF is

The answer is 6. It's an equilateral triangle
Let the intersection of BD and EF be o
BD=2√3,DO=√3,
And DC = √ 3,
It is proved that the triangle DOF and DCF are congruent,
Therefore, ∠ ODF = ∠ FDC = ∠ ODC / 2 = 60 / 2 = 30 degree
So DF = 2
Because do bisects EDF, and vertical EF,
So Ed = DF, and the included angle is 60 degrees
This is an equilateral triangle with two sides

How to convert the speed unit is to convert cm / s DM / s to m / s km / s, for example: 50c
How to convert speed units is to convert cm / s DM / s into m / s km / s, for example: 50cm / S = km / h, 20dm / S = km / h,

50cm/s=(50/100000km)/(1/3600h)=1.8km/h
20dm/s=(20/10000km)/(1/3600h)=7.2km/h

100 mathematical calculation questions and answers in grade one of junior high school

The circumference of a rectangle is four meters, one of which is four eleventh of a meter wide, and one of which is one tenth of a meter long

Length = 4 △ 2-4 / 11 = 18 / 11 m = 18 / 11 m

Calculate (1-3) × (3-5) / (5-7) × (7-9) / (9-11) × (11-13) / (2005-2007)

Original formula = (1-3) × [(3-5) / (5-7)] × [(7-9) / (9-11)] ×. × [(2001-2003) / (2005-2007)]
=(-2)×1×1×.×1
=-2

It takes 36 seconds for a train to pass the 1500 meter long bridge and 4 seconds for it to pass the sentry at the end of the bridge. What is the length of the train______ Rice

Let the length of the car be X. since it takes 4 seconds to pass the sentry at the bridge head, the following equation X4 = 1500 + X36 can be solved to get x = 187.5, so the answer is 187.5 meters

The perimeter of a rectangle is 240cm, and the ratio of length to width is 3:1. The area of the rectangle is______ Square centimeter

The sum of length and width: 240 △ 2 = 120 (CM); the total number of parts of length and width: 3 + 1 = 4 (CM); length: 120 × 34 = 90 (CM); width: 120 × 14 = 30 (CM); the area of rectangle: 90 × 30 = 2700 (CM); answer: the area of rectangle is 2700 square cm. So the answer is: 2700