The clock angle is 105 degrees at 2:30 Why?

The clock angle is 105 degrees at 2:30 Why?

The hour hand moves 360 / 12 / 60 = 0.5 ° per minute
2 clockwise to 60 degrees
2:30 points to 60 + 0.5x30 = 75 degrees
The minute hand is 180 degrees
So the difference is 105 degrees
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The time indication on the clock is 2:30, and the angle between its clock and minute hand is ()
A、150° B、135° C、120° D、105°
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C
One minute is six degrees

From 2:30 to 2:55, how many degrees does the clock rotate in minutes?

Minute hand: 150 degrees
Hour hand: 12.5 degrees

1. If the quotient of natural number a divided by natural number B is 10, then the greatest common divisor of a and B is ()
A、a B、b C、10
2. A triangle is divided into two triangles by drawing a line segment through one of its vertices. The sum of the inner angles of one of the triangles is ()
A. 180 ° B, 90 ° C, uncertainty
3. It takes 10 hours for a bus and 15 hours for a truck to drive from a to B. the speed ratio of a bus to a truck is ()
A、2：3 B、3：2 C、2：5
4. Three 12 decimeter long wires are used to form rectangle, square and circle
A. Rectangle B, square C, circle
5. In the division equation m △ n = a In B, (n ≠ 0), the following formula is correct ()
A、a＞n B、n＞a C、n＞b
6. If you pass a vertex of a parallelogram to the opposite side, you can make () height
A. 1 B, 2 C, 5
7. Three lead wires of the same length are used to form a circle, a square and a rectangle respectively
A. Circle B, square C, rectangle
8. The ratio of number a to number B is 0.4, and the ratio of number B to number a is ()
A.0.4 B.2.5 C.2/5
9. After processing a batch of parts, 100 of them are qualified and 25 of them are unqualified. The qualified rate of this batch of parts is ()
A、75% B、80% C、100%
10. The third digit to the right of the decimal point is ()
A. Percentile B, thousandth C, 0.01 D, 0.001
11. The volume of a cylinder with equal base and height ()
A. Big B, big 2 times C, small
12. If 4x = 3Y, then x and Y ()
A. Positive proportion B, negative proportion C, out of proportion
13. If the quotient is 2, then the remainder is ()
A、1 B、0.1 C、0.01 D、10
14. To make a batch of parts, if everyone's work efficiency is certain, then the number of workers and the time spent ()
A. In proportion B. in inverse proportion C. out of proportion
15. For two ropes of the same length, one is cut 3 / 7, the other is cut 3 / 7 meters, and the () one is longer
A. The first length B, the second length C, the same length d, unable to judge
16. A piece of rope is cut into two sections. The first section is 3 / 7 meters long, the second section accounts for 3 / 7 of the total length, and the () section is longer
A. The length of the first segment is B, the length of the second segment is C, and the length of the same segment is d

Maybe I did something wrong, but I have tried my best_ O ~ 1, natural number a divided by natural number B, the quotient is 10, then the greatest common divisor of a and B is (b). A, a, B, B, C, 102, a triangle, draw a line through one of its vertices, and divide it into two triangles, one of which is

A cylinder with a height of 15 cm, if its height increases by 2 cm, its surface area will increase by 125.6 square cm?

The original circumference of the bottom of the cylinder is: 125.6 △ 2 = 62.8 cm
The original bottom radius of the cylinder is 62.8 △ 3.14 △ 2 = 10 cm
The original volume of the cylinder is: 3.14 × 10 × 10 × 15 = 4710 cubic centimeters

"Light year is a unit of length used in astronomy. It represents the distance that light travels in a vacuum for one year: how many kilometers is a light year? Vega, the star closer to us, is about 27 light-years away from the earth. How many kilometers is Vega away from the earth?

The distance of light propagation in a year: S = VT = 3 × 108m / s × 365 × 24 × 3600s ≈ 9.46 × 1015m = 9.46 × 1012km; the distance between Vega and the earth: s' = s × 27 = 9.46 × 1012km × 27 ≈ 2.55 × 1014km. A: one light year equals 9.46 × 1012km; Vega is 2.55 × 1014km away from the earth

The bicycle starts to advance at an acceleration of 1 m / S ^ 2 from a standstill. At the same time, someone pursues the bicycle 25 m behind the bicycle at a speed of 6 m / s. can the person chase the bicycle at a constant speed? If not, what is the minimum distance between the fingers?

This problem should be solved in this way
First, find out the time when the bicycle speed reaches 6m / s, even if the distance between the two at the same speed is required
If the time is 6S, the catch-up movement is 36m, and the cycling movement is 1 / 2 at & sup2; = 18m
Obviously, 18 + 25 > 36, so when the speed of the two is the same, they haven't caught up with each other, so they won't catch up with each other in the future
This way of thinking will not be easy to make mistakes, do not have to assume catch up or not catch up
The process becomes a program

If the length and width of a rectangle are increased by 3cm, its area will be increased by 105 square cm. What is the perimeter of the original rectangle?
Write down the process and why

105-3 × 3 = 96 square centimeter
96 △ 3 = 32 cm
Perimeter: 32 × 2 = 64 cm

1-3:1-12:7 + 20:9-30:11 + 42:13-56:15?

It's 1 + 3:1-12:7 + 20:9-30:11 + 42:13-56:15-12:7 + 20:9-30:11 + 42:13-56:15 = - 7 / 12 + 9 / 20-11 / 30 + 13 / 42-15 / 56 = - (3 + 4) / (3 * 4) + (4 + 5) / (4 * 5) / (5 * 6) + (6 + 7) / (6 * 7) - (7 + 8) / (7

The range of function f (x) = 3 / 3 ^ x-3

If f '(x) = - 3ln3 * 3 ^ (- x) is derived from it, because 3 ^ (- 3) is always positive, we can know that f' (x) is always negative, so f (x) is monotonically decreasing. Then when x is negative infinity, f (x) is positive infinity, and when x is positive infinity, f (x) is - 3, and the range is - 3 to positive infinity