Expressed by scientific notation: - 0.001685 ≈__________ (keep two significant numbers)

Expressed by scientific notation: - 0.001685 ≈__________ (keep two significant numbers)

- 3 power of 1.7 * 10

One day, Xiaohong and Xiaoli used the temperature difference to measure the height of the mountain. Xiaohong measured the temperature at the top of the mountain to be - 1 ℃, and Xiaoli measured the temperature at the foot of the mountain to be 5 ℃. It is known that every 100 meters increase in the height of the area, the temperature will decrease by about 0.8 ℃. How many meters is the height of the mountain?

Suppose that the height of the peak is about X meters, according to the meaning of the title: 5-x100 × 0.8 = - 1, the solution is: x = 750;

1. It is known that the midpoint o of the parallelogram ABCD is any point on the diagonal, and the parallels EF and Mn passing through the point o are two groups of sides. The area relationship between the parallelogram bnoe and the parallelogram dnof is conjectured, and the reasons are explained
2. As shown in the figure, known parallelogram ABCD, AE bisects ∠ bad, AE divides DC into 8 and 10 parts, try to find the perimeter of parallelogram ABCD
7. As shown in the figure, in the parallelogram ABCD, ab = be, connect AE and extend the intersection of the extension line with DC and point F, ∠ f = 62 ° to find the degree of each internal angle of the parallelogram ABCD
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1. If O is on AC, there are known conditions for a quadrilateral amoe and CFon to be a parallelogram. It is easy to prove that s-triangle amo = s-triangle AEO, s-triangle CFO = s-triangle CNO. Because s-triangle ABC = s-triangle ADC, s-quadrilateral bnoe = s-quadrilateral dmof2ab = 18

Simple calculation of 8.27-1.12 + 0.15-0.36 + 1.73 + 4.85-2.25

8.27-1.12+0.15-0.36+1.73+4.85-2.25
=（8.27+1.73）+（0.15+4.85）+（-1.12-0.36-2.25）
=10+5-3.73
=11.27

For the approximate number expressed by scientific counting method, the significant number of () is the significant number of this approximate number. To determine the exact position of the approximate number expressed by scientific counting method, we should first restore the number expressed by scientific counting method to the original number, and then see which position of () is in the restored number, that is, the exact position
Attention, it's scientific counting!

For the approximate number expressed by scientific counting method, the significant number of (a) is the significant number of this approximate number. If the approximate number expressed by scientific counting method is required to be accurate, the number expressed by scientific counting method should be restored to the original number first, and then the last bit of (a) should be in the restored number, that is, the exact position

As shown in the figure, a, B, C and D are the four vertices of the rectangle, ab = 16cm and ad = 6cm. The moving points P and Q start from point a and C at the same time. Point P moves to point B at the speed of 3cm / s until it reaches B, and point Q moves to D at the speed of 2 & nbsp; cm / S. (1) how many seconds does P and Q start from the start? The area of quadrilateral pbcq is 33cm2; (2) from the start of P and Q to a few seconds? The distance between point P and point q is 10 cm

(1) Let P and Q have an area of 33cm2 from the start to x seconds, then Pb = (16-3x) cm, QC = 2xcm. According to the trapezoidal area formula, we get 12 (16-3x + 2x) × 6 = 33, and the solution is x = 5. (2) let P and Q have a distance of 10cm from the start to x seconds, then QE ⊥ AB, perpendicular foot e, QE = ad = 6, PQ = 10, ∵ PA = 3T, CQ = be = 2T, ∵ PE = ab-ap-be = | 16-5 T |, from Pythagorean theorem, we get (16-5t) 2 + 62 = 102, the solution is T1 = 4.8, T2 = 1.6. Answer: (1) the area of quadrilateral pbcq is 33cm2 when P and Q start from the starting point to 5 seconds; (2) when P and Q start from the starting point to 1.6 seconds or 4.8 seconds, the distance between P and Q is 10cm

25 × 24 × 125 = simple calculation

25X4x6x125=75000

On the meaning of "odd over even" in the method of number axis through root

The meaning of odd over even is very simple. The root of the singular term passes through the number axis. The root of the even term passes through the number axis

As shown in the figure, in square ABCD, e is the midpoint of AD, G is the point above DC, and DG = 14dc, is be perpendicular to eg?

It is proved that: let the side length of square ABCD be a, and then calculate eg = 54a in RT △ deg. similarly, be = 52A, BG = 54a, ∵ EG2 + be2 = (54a) 2 + (52A) 2 = 2516a2, BG2 = (54a) 2 = 2516a2, ∵ EG2 + be2 = BG2, ∵ be is a right triangle, and ∵ be is perpendicular to eg

Power = () the third power of DM, the third power of 1dm = () L. the third power of 1cm = () ml
1km = (), 1m = () DM = () cm = () mm, 1m = () um = () nm, the third power of 1m = () DM, the third power of 1dm = () l.1cm = () ml

1km=(1000)m,1m=(10)dm=(100)cm=(1000)mm,1m=(10^6)um=(^9)nm.
The power of 1 m is the power of (1000) DM, the power of 1 DM is the power of (1) l, and the power of 1 cm is the power of (1) ml