The clock indicates 2:15. What is the acute angle between its hour hand and minute hand? The minute hand of the clock goes every minute: 360 / 60 = 6 degrees, Hour hand per minute: 360 / 12 / 60 = 0.5 degrees, So at 2:15, the angle between the hour hand and 12:00 is 0.5 * 15 + 2 * 30 = 67.5 degrees, The angle between the minute hand and 12 o'clock is: 6 * 15 = 90 degrees, Therefore, the acute angle between the hour hand and minute hand is 90-67.5 = 22.5 degrees This is the answer. But I still don't understand! "At 2:15, the angle between the hour hand and 12:00 is 0.5 * 15 + 2 * 30 = 67.5 degrees." Why 0.5 * 15 + 2 * 30,

The correct solution is as follows
1. At 2:15, the angle between the minute hand and 12:00 is 90 degrees, which is very easy to understand
2. At 2 o'clock, the angle between the position of the hour hand and 12 o'clock is (360 / 12) X2, which is 60 degrees!
3. Ask for the angle between the two hands at 2:15. In the 15 minutes after 2:00, the clock moves 0.5x15, that is 7.5 degrees. Note that it moves again! So at 2:15, the angle between the clock and 12:00 is 60 + 7.5, that is 67.5 degrees!
4. In the end, it's very simple. Subtract the angle between the minute hand and 12 o'clock from the angle between the hour hand and 12 o'clock, which is 90-67.5. The answer is 22.5 degrees!
I don't know if my explanation is clear. If you think it's good, can you add some points?

How many degrees did the clock turn from 2:15 to 5:30

Turn the clock for 1 hour = 360 ° 12 = 30 degree
Time from 2:15 to 5:30 = 5.5-2.25 = 3.25 hours
So:
Rotation degree = 30 °× 3.25 = 97.5 degree

At 2:30 p.m., the angle between the minute hand of the clock and the hour hand is degrees______ ．

∵ the hour hand turns 0.5 ° per minute on the clock face, and the minute hand turns 6 ° per minute. ∵ at 2:30 p.m., the angle between the hour hand and the minute hand can be regarded as 0.5 ° × 30 = 15 ° when the hour hand turns 2:30 p.m., and the minute hand is on the number 6. ∵ there are 12 numbers on the clock, and the angle between each two adjacent numbers is 30 °, and the angle between the minute hand and the hour hand is 4 × 30 ° - 15 ° at 2:30 p.m. = 105 °

Surface area and volume formula of prism and cylinder, sphere, cone and pyramid

Prism surface area a = L * H + 2 * s, Volume V = s * H (L - base perimeter, H - column height, s - base area), cylinder surface area a = L * H + 2 * s = 2 π * r * H + 2 π * R ^ 2, volume v = s * H = π * R ^ 2 * H (L - base perimeter, H - column height, s - base area, R - base circle radius), sphere surface area a = 4 π * R ^ 2, Volume V = 4 / 3 π * R ^ 3 (R

A rectangle, four fifths of its length and one-half of its width, its perimeter and area! It's a process! It's urgent!

Four fifths plus one half times two area: one fifths and one half

Use the rounding method to approximate the following numbers according to the requirements in brackets
(1) 245.635 (accurate to 0.1) (2) 175.65 (accurate to individual position) (3) 12.004 (accurate to hundred position) (4) 6.5378 (accurate to 0.01)

(1)245.6
(2)176
(3)12.00
(4)6.54
PS. do you want to say accurate to the percentile?

A train is 180m long and passes through a 600m long tunnel at a constant speed of 20m / s. The time required for all trains to pass through the tunnel is calculated

（180+600）/20=780/20=39s

In the figure, ABCD is a rectangle. The area of triangle EFD is 6 square centimeters larger than that of triangle ABF. Is BC = 6? CD equals 4 cm. Find the length of ED

The triangle BCE area s = the area of rectangle ABCD + 6 = 1 / 2 * BC * ce, so BC * CD + 6 = 1 / 2 * BC * (ED + CD) 6 * 4 + 6 = 1 / 2 * 6 * (ED + 4) 30 = 3Ed + 12 ed = 18 / 3 ed = 6

What is the unit of length larger than kilometer?

The greater unit of length for a kilometer is ten thousand meters

According to the regulations of Beijing's telephone monthly charge, the monthly rent is 25 yuan, and the call is counted every three minutes. If the call is less than three minutes, it is counted once, and the charge is 0.18 yuan each time. (1) if the monthly telephone charge is m yuan, ask the user to pay the charge formula of M yuan and N times; (2) if the user makes 47 calls in a month, how much should he pay? (3) If the user paid 30.4 yuan, how many calls did the user make?

(1) M = 0.18n + 25 (2 points) (2) when n = 47, M = 0.18 × 47 + 25 = 33.46 (yuan) (3 points) (3) when m = 30.4, 30.4 = 25 + 0.18n (4 points) ‖ n = 30 (Times) (5 points) a: 30 calls. (6 points)