Xiao Li's family will travel from Xi'an to Harbin, while Xiao Hua's family will go on holiday from Harbin to Xi'an Xiaoli's family will travel from Xi'an to Harbin, and Xiaohua's family will take a vacation from Harbin to Xi'an. The railway from Xi'an to Harbin is about 2600 kilometers long. At 8 a.m. on New Year's day, Xiaoli's family will start from Xi'an by train, which runs 60 kilometers per hour. At the same time, Xiaohua's family will start from Harbin by train, which runs 70 kilometers per hour, The two trains meet?

After X hours, the two trains meet
60x+70x=2600
130x=2600
x=20
A: after about 20 hours, the two trains met
2600 / (60 + 70) = 2600 / 130 = 20 hours
20 hours
2600/130=20
The equation?
It takes about X hours.
60X+70X=2600
130X=2600
X=20
The calculation method is as follows:
2600 / (60 + 70) = 2600 / 130 = 20 hours
If the train line is the same, it will take 20 hours? I'll raise the reward
The money ratio of Xiaohong and Xiaoli is 8:7. Xiaohong gives Xiaoli 8 yuan, and their money ratio is 4:5. How much do they have
Let Xiaohong's money number be 8x and Xiaoli's money number be 7x. The equation is as follows: (8x-8) 4 = (7x + 8) 5. The solution is x = 6, so Xiaohong is 48 yuan and Xiaoli is 42 yuan
PEP primary school mathematics oral arithmetic training sixth grade volume I answers
Number: Yes
It is known that the sum of the first n terms of the arithmetic sequence an is Sn and satisfies A2 + A4 = 6 and S7 = 28
1. Find the formula of an general term
2, the sequence BN satisfies an = [B1 + 2B2 + 2 ^ 2 B3 + +2 ^ (n-1) BN] / N to find the sum of the first n terms of sequence BN
The second question is, you suck up!
(1) To find the first n terms and Sn (2) of sequence an, try to find all positive integers m, so that am * a (M + 1) / a (let an = a + (n-1) d, D is not equal to 0 (A2) ^ 2 + (A3) ^ 2 = (A4) ^ 2 + (A5) ^ 2)
a1+d+a1+3d=6
7a1+42d=28
Solve a and D to write the general term
The second question is optional
1. Because A2 + A4 = 6, so 2A3 = 6, so A3 = 3
And because S7 = 28, so 7a4 = 28 (this is a formula), so A4 = 4
An=n
2. The positions of an and BN are wrong
Let A1 and tolerance Q be 2A1 + 4q = 6 from equation 1, 7a1 + 21q = 28 from equation 2, A1 = 1 from solution, q = 1, an = a1 + (n-1) q = n
The second question hasn't come up yet
What is the unit of electric work formula
Sometimes, if you can't figure out the number of units plus kilowatt hour, it's still coke
1kwh = 1000W × 3600s = 3600000 joules
See the title to the unit, generally first into coke, if necessary, converted into kilowatt hours
It should be in units of energy: joules
Do you have oral math problems in grade six
Sixth grade first semester
17×40＝ 100－63＝ 3.2＋1.68＝ 2.8×0.4＝ 14－7.4＝ 1.92÷0.04＝ 0.32×500＝ 0.65＋4.35＝ 10－5.4＝ 4÷20＝ 3.5×200＝ 1.5－0.06＝ 0.75÷15＝ 0.4×0.8＝ 4×0.25＝ 0.36＋1.54＝ 1.01×99＝ 420÷35＝ 25...
Let the sum of the first n terms of the arithmetic sequence {an} be Sn, and A3 = 5, S15 = 225. (I) find the general term an of the sequence {an}; (II) let BN = 2An + 2n, find the sum of the first n terms and TN of the sequence {BN}
(I) let the first term of the arithmetic sequence {an} be A1, and the tolerance be d. from the meaning of the problem, we get a1 + 2D = 515a1 + 15 × 142d = 225, and the solution is A1 = 1D = 2, an = 2N-1; (II) BN = 2An + 2n = 12.4n + 2n, TN = B1 + B2 + +bn=12（4+42+… +4n）+2（1+2+… +n）=4n+1−46+n2+n=23•4n+n2+n−23．
What is the physical knowledge inventory of grade two about electric energy and electric heating
Electric work and electrothermal knowledge induction: 1. Electric work (W): the work done by current is called electric work. 2. Unit of electric work: international unit: Joule. Common units are: Degree (KWH), 1 degree = 1 kwh = 3.6 × 106 Joule. 3. Tool for measuring electric work: electric energy meter. 4. Calculation formula of electric work: w = uit
Mathematics in Grade 6 of primary school oral arithmetic (New)
3 minus 1 and 1 / 5 divided by 2.4 =?
5 times 1 / 8 plus 0.25 =?
8 and 7 / 8 minus (0.875 minus 4 / 7) =?
1 and 1 / 5 minus 0
3 / 4 times 99 plus 0.75 =?
1 / 10 times 10% times 0.1 =?
3 and 3 / 4 divided by 5 times 4 / 5 =?
2/3 7/8(0.875) 17/56 1/5 100 0.001 75/16
3-1.2/2.4=2.5
5*1/8+0.25=40.25
8.7/8 -(7/8-4/7)=8.4/7
1.1/5-0.85-3/20= 1/5
3/4*99+0.75 =75
1/10* 10% * 1/10= 1/1000
3.3/4 /5 * 4/5=3/5
3 minus 1 and 1 / 5 divided by 2.4 = 2.5
5 times 1 / 8 plus 0.25 = 40.25
8 and 7 / 8 minus (0.875 minus 4 / 7) = 463 / 56
1 and 1 / 5 minus 0.85 minus 3 / 20 = 1 / 5
3 / 4 times 99 plus 0.75 = 75
1 / 10 times 10% times 0. 1 = 1 / 1000
3 and 3 / 4 divided by 5 times 4 / 5 = 3 / 5
Let {an + Sn} be the sum of the first three terms of the sequence of numbers, and let an = 3
solution
An is equal difference
s5=(a1+a5)*5/2=30
∴a1+a5=12
And a1 + a3 = 8
Subtraction of two formulas
a5-a3=2d=4
∴d=2
∴a1+a3=2a1+2d=8
∴a1=2
∴an=2+(n-1)*2=2n
S5=5a3=30
a3=6
a1+a3=8
a1=2
a3=a1+2d
6=2+2d
D=2
An = 2 + (n-1) * 2 = 2n question: remember BN = 2An, find the first n terms and TN of the sequence {BN}. Please help to solve the second question. Thank you, please

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