The math problem of volume two of grade six is so urgent! About the operation of numbers. 0 A road construction team needs to build a 2100 meter long highway, with an average of 240 meters per day in the first five days. The remaining tasks need to be completed in three days, with an average of how many meters per day? There is a barrel of oil. Two fifths of it has been used up, and there are still 48 kilograms left in the barrel. How many kilograms does the barrel weigh? According to the regulations of the postal department, the postage is 1.2 yuan for every 20 grams of a letter. The letter sent by my father weighs 35 grams. How much is the postage? One more: Fill in the number according to the rule. ① 81、64、49、36、【 】、【 】 ② 35、28、22、17、【 】、【 】、 ③ 1、2、4、7、11、【 】、【 】、 ④ 2、3、5、8、【 】、【 】、 ⑤ 2、3、4、9、6、27、【 】、【 】、

The math problem of volume two of grade six is so urgent! About the operation of numbers. 0 A road construction team needs to build a 2100 meter long highway, with an average of 240 meters per day in the first five days. The remaining tasks need to be completed in three days, with an average of how many meters per day? There is a barrel of oil. Two fifths of it has been used up, and there are still 48 kilograms left in the barrel. How many kilograms does the barrel weigh? According to the regulations of the postal department, the postage is 1.2 yuan for every 20 grams of a letter. The letter sent by my father weighs 35 grams. How much is the postage? One more: Fill in the number according to the rule. ① 81、64、49、36、【 】、【 】 ② 35、28、22、17、【 】、【 】、 ③ 1、2、4、7、11、【 】、【 】、 ④ 2、3、5、8、【 】、【 】、 ⑤ 2、3、4、9、6、27、【 】、【 】、

First question:
（2100-5×240）÷3=300
Or X × 3 + 5 × 240 = 2100
Second question
48÷（1-2/5）=80
The third question
1.2×2=2.4

Mathematics problems in Volume 2 of grade 6
Count one formula for B and one formula for a
1. A is three-quarters of B. when a is increased by 6, the ratio of a to B is 3:2. What is the original value of a and B?

Let B be x, then a be 3 / 4x
（3/4x + 6 ）/ x =3：2
The solution is x = 8
So a = 6, B = 8
In the formula, "/" is a semicolon

1. There are two equal bottomed cylinders. If the height of cylinder a is three fifths of that of cylinder B, what is the volume of cylinder a?
2. To cut a cube wood block whose edge length is 2 mm into the largest cylinder, you need to cut () cubic decimeter wood block
3. The area of the bottom of a cylinder is 2 times of the original, the height is 4 times of the original, and the volume is () times of the original

1. Three fifths (no process)
2.2*2*2-(1*1*3.14*2)=1.72
3.2*4=8