Simple calculation: 1 / 2 + 1 / 3 + 2 / 3 + 1 / 4 + 2 / 4 + 3 / 4 + ＋1/60＋2/60＋3/60＋… ＋59/60

Simple calculation: 1 / 2 + 1 / 3 + 2 / 3 + 1 / 4 + 2 / 4 + 3 / 4 + ＋1/60＋2/60＋3/60＋… ＋59/60

1/2+1/3+2/3+1/4+2/4+3/4+1/5+2/5+3/5+4/5+1/6+…… +1/60+2/60+3/60+…… +59/60
=(1/2)+(1/3+2/3)+(1/4+2/4+3/4)+...+(1/60+2/60+...+59/60)
The general formula is 1 / 2 + 1 / 3 + 2 / 3 + 1 / 4 + 2 / 4 + 3 / 4 + 1 / 5 + 2 / 5 + 3 / 5 + 4 / 5 + 1 / 6 + +1/a+2/a+...+(a-1)/a
=(1/2)+(2/2)+(3/2)+...+((a-1)/2)
=(1+2+3+4+...+(a-1))/2
=(1+2+3+4+..+59)/2
=59(1+59)/4
=59*15
=885

1+1/2+1/3+2/3+1/4+2/4+3/4+...59/60

1/n+2/n+…… +(n-1)/n
=([1+2+…… +(n-1)]/n
=[n(n-1)/2]/n
=(n-1)/2
So the original formula = 1 + 1 / 2 + 2 / 2 + 3 / 2 + +59/2
=1+(1+2+…… +59)/2
=1771

How to calculate 1 * 2 + 2 * 3 + 3 * 4 + 4 * 5 +. + 59 * 60

1*(1+1)+2*(2+1)+.+59(59+1)
=(1+2+3+...+59)+(1^2+2^2+...+59^2)
=(1+59)*59/2+59(59+1)(2*59+1)/6
＝71980

There are four Thursdays and five Wednesdays in August of a certain year. What is August 8 of that year
This is a mathematical question to fill in the blanks

Because there are 31 days in August, five Wednesdays can only be in the following three situations: (7 days apart, same number of weeks)
1, 8, 15, 22, 29
2, 9, 16, 23, 30
3, 10, 17, 24, 31
Then, there are only four Thursdays in this month, so only the third one fits. So the 10th is Wednesday, and the 8th must be Monday

Chemical literal expression and symbolic expression
1. Hydrogen burns in air
2. Copper is heated in air

1. Literal expression: hydrogen + oxygen ignition → water
Chemical equation: 2h2 + O2 = ignition = 2H2O
2. Literal expression: Copper + oxygen - heating → copper oxide
Chemical equation: 2Cu + O2 = heating = 2CuO

What are the concepts of 1000 square meters and 1 square kilometer?

One square kilometer is 1000X1000 = 1 million square meters, and 1000 square meters is only 1000 square meters

If the tax rate is adjusted from B% to C%, and the purchase price and profit of the commodity remain unchanged, then the selling price of the commodity is the original___ ．

Let profit be a, purchase price be n, the original selling price be x, and the present selling price be y. ∵ profit = selling price purchase price x tax rate, the original tax rate is B%, ∵ a = x-n-b% x, x = a + n1-b%. Similarly, y = a + n1-c%, ∵ X: y = a + n1-b%: a + n1-c% = 1-B% 1-C%, so the answer is: 1-B% 1-C%

180°-52°18′36″-25°36″*4

180°-52°18′36″-25°36″*4 =180°-52°18′36″-100°144″=180°-52°18′36″-100°2‘24″=180°-(52°18′36″+100°2‘24″)=180°-152°20′60″=180°-152°21′=179°60'-152°21′=27°39...

X ^ 2-4x + 4 of x ^ 2-4

x^2-4x+4 = (x-2)^2
x^2-4 = (x-2)(x+2)
So it's about (X-2) to (x + 2)

If a times 1 / 9 = B times 5 = C times 1 / C (C is not equal to 0), then a and B are

1. The product of a number and its reciprocal is 1, so a = 9 / 5-1 = 4 / 5
2. C multiplied by 1 / C (C is not equal to 0) = 1, so a = 9, B = 1 / 5