Four mathematical calculation problems 1. Find the rules 13 6.5 （ ） 1.625 （ ） 2. Calculation (3 courses) （1）2.5×0.77×0.4 （2）（8-0.8）×12.5 （3）1.9×4.5+0.45

Four mathematical calculation problems 1. Find the rules 13 6.5 （ ） 1.625 （ ） 2. Calculation (3 courses) （1）2.5×0.77×0.4 （2）（8-0.8）×12.5 （3）1.9×4.5+0.45

1. Find the Rule 13 6.5 (3.25) 1.625 (0.8125) 2. Calculate (3 tracks) (1) 2.5 × 0.77 × 0.4 = 2.5 × 0.4 × 0.77 = 1 × 0.77 = 0.77 (2) (8-0.8) × 12.5 = 8 × 1.25-0.8 × 12.5 = 10-1 = 9 (3) 1.9 × 4.5 + 0.45 = 19 × 0.45 + 0.45 = (1 + 19) × 0.45 = 20 × 0

A super difficult calculation problem (with simple algorithm)
2006 △ 2006 and 2006 / 2007 =?
2006 / 2007: 2006 / 2007
If you don't know anything else, please ask

2006 / (2006+2006/2007)
=1/(1+1/2007)
=1/(2008/2007)
=2007/2008

Help me calculate, a calculation problem, there should be a simple algorithm, right
37.5×21.5×0.112+35.5×12.5×0.112

37.5×21.5×0.112+35.5×12.5×0.112 =0.112×（37.5×21.5+35.5×12.5） =0.112×（12.5×3×21.5+35.5×12.5） =0.112×12.5×（3×21.5+35.5） =0.112×12.5×100 =1250×（0.1+0.01+0.002） =125+12.5+2.5 =140...

The second grade of junior high school
There are two roads from a to B, each of which is 3km. The first road is a level road. The next day, there are 1km uphill road and 2km downhill road. Xiaogang's riding speed on the uphill road is a km / h, the riding speed on the level road is 2akm / h, and the riding speed on the downhill road is 3akm / h, How long does it take for him to get from a to B? (2) which road does he take less time from a to B? How much less time?

T2 = 1 / a = 2 / 3A = 5 / 3A 2. The first road T1 = 3 / 2a, the first time-consuming road T1 = 5 / 3a-3 / 2A = a

About fraction
When Xiao Ming goes uphill after school, the speed is m km / h; when he returns home from school, the speed is n km / h, then the average speed of Xiao Ming at school and after school is?

We set the distance between Xiaoming's home and school as X km, then the total distance between school and school is 2x km
It takes X / M hours to go to school when m km per hour
It takes X / N hours to finish school when it is n kilometers per hour
The total distance is 2x km, and the total time is x / M + X / N = (M + n) x / Mn hours
The total distance divided by the total time is the average speed, which is 2 Mn / M + n km / h
Remember not to use (M + n) / 2

If B + 1C = 1, C + 1A = 1, find the value of AB + 1b

∵b+1c＝1，∴b＝1−1c=c−1c；∵c+1a＝1，∴a＝11−c；∴ab+1b=a+1b=11−c+cc−1=1．

Fraction class
The original price of a commodity is a yuan, but it still makes a profit of B% after 20% discount. What's the purchase price of this commodity?

What's the profit percentage = (selling price - purchase price) / (purchase price is 20% discount, so the selling price should be multiplied by 0.8b%, which can be expressed as B / 100. Suppose that the purchase price of the commodity is x (0.8a-x) / x = B / 100, two sides multiply by x0.8a-x = BX / 100, two sides multiply by 10080a-100x = BX, move item 100x + BX = 80A (100 + b) x = 80ax = 80A / (100 + b)

Mathematical problems in the second fraction of junior high school
(a ^ 2-1 / A ^ 2-5A + 6) / (a ^ 2 + A-2 / A-3) - (a + 3 / A ^ 2-4) how to simplify / is the fraction line a fraction minus the following fraction? Thank you. Do you understand

Take a picture, OK? I don't understand

Primary school mathematics under the fifth grade mathematics Evaluation Handbook p53 answers
Xiaohua finished reading a story book in three days, two fifths of the total pages in the first and second days, nine tenths of the total pages in the second and third days?

Two fifths plus nine tenths is thirteen tenths
Thirteen tenths minus one gets three tenths
A: the next day accounts for three tenths
Give me the best answer

Handbook of mathematics evaluation
My homework is eight mathematical evaluation manual, but I forgot, only 40 to 41 pages
Just one, three, five

x=6 x=11/4 -5 c d