As shown in the figure on the right, it is a rectangular timber with a square cross section Xiaoming's water consumption in January was 5 / 2 tons, which was 1 / 5 less than that in January. How many tons of water will be saved in February? Xiaoming's water consumption in January was 5 / 2 tons, which was 1 / 5 tons less than that in January. How many tons of water will be saved in February? Please pay attention to the words

Xiao Ming's water consumption in January is 5 / 2 tons, which is 1 / 5 less than that in January. How many tons of water can be saved in February? 5 / 2 times 1 / 5 equals 1 / 2 A: 1 / 2 tons of water can be saved in February. Xiao Ming's water consumption in January is 5 / 2 tons, which is 5 / 5 less than that in January

Known 5 cubic meters of wood weight 3 tons, 1.8 tons of wood volume is how much

1.8 / (3 / 5) = 3 m3

A cuboid timber, the volume is 0.078 cubic meters, known timber width 2 decimeters, this timber length how many decimeters?

0.078 m³ = 0.078×1000 dm³ = 78 dm³
78 ÷2÷3 =13 （dm）
A: the wood is 13 decimeters long

0.8 * (125 + 12.5 + 1.25) (simple calculation)

0.8*（125+12.5+1.25）
=0.8x125+0.8x12.5+0.8x1.25
=100+10+1
=111

Application of grouping summation method
Sn＝（1＋1）＋[a^(-1)+4]＋[a^(-2)+7]＋…… + [a ^ (1-N) + (3n-2)], find the sum of the first n terms
p. S. it's better to write the answer,

Sn ＝（1＋1）＋[a^(-1)+4]＋[a^(-2)+7]＋…… ＋[a^(1-n)+(3n-2)] ＝[1＋a^(-1)+a^(-2)＋…… ＋a^(1-n)] + [1＋4＋7+…… + (3n-2)] the former is equal ratio sequence, the common ratio is a ^ (- 1), the latter is equal difference sequence, the tolerance is 3 = [1-A ^ (- n)] / (1-A) + [1 + (3n-2)

If the function f (x) = a ^| 2X-4 | (a > 0, a is not equal to 1) satisfies f (1) = 1 / 9, then the monotone decreasing interval of F (x) is

f(x)=a^|2x-4|
x=1
a^2=1/9
a=1/3
f(x)=(1/3)^|2x-4|
The monotone decreasing interval of F (x) is the increasing interval of | 2X-4 | (2, + ∝)

The greatest common divisor and the least common multiple of 48 and 18

The greatest common divisor is 6
The least common multiple is 48 × 18 △ 6 = 144

If three points a (2,2) B (a, 0) C (0, b) where the range of a and B is 0 to infinity, what is the minimum value of AB

If it's three points on a straight line
Let y = NX + M
Bring in three points
m=b;2n+m=2;an+m=0;
That is: 2n + B = 2; n = (2-B) / 2;
[(2-b)/2]*a+b=0;
2a-ab+2b=0;
ab=2(a+b);
A + b > = 2 * sqrt (AB) (double radical AB)
ab=2(a+b)>=4*sqrt(ab)
sqrt(ab)>=4
ab>=16

How to find the n-order derivative of y = sin (3x + 2) y

Xiaohua did a problem: calculate 15 / (1 / 5-1 / 3) = 15 / 1 / 5-15 / 1 / 3 = 15 * 5-15 * 3 = 75-45 = 30, do you think Xiaohua's solution is correct
If not, how to correct it

Incorrect, the value of 1 / 5-1 / 3 should be calculated first, that is - 2 / 15
Then the original formula = 15 / (- 2 / 15) = 15 * (- 15 / 2) = - 225 / 2