简便计算 (1) × ﹣ × (2) 3.78+3.2+7.22+6.8 (3) 2.37÷8÷1.25 答案:解:35×137-37×35 =35×(137-37) =35×107 =67
解:3.78+3.2+7.22+6.8 =(3.78+7.22)+(3.2+6.8) =11+10 =21
解:2.37÷8÷1.25 =2.37÷(8×1.25) =2.37÷10 =0.23723、LONDON—The tiny, distant and
frozen planet Pluto, for 30 years believed to have just one moon, has suddenly
been found to have two more satellites.
Only discovered in 1930 because of its vast distance from Earth, Pluto has
remained a largely mysterious object ever since.
Some three billion miles from the Sun, Pluto, a dwarf planet, remains to be
visited by a spacecraft.
Its first known satellite is called Charon. With a diameter of 1,200 km, it is
half that of Pluto—unusually
large for a moon in relation to its primary.
But now, using images from the Hubble Space Telescope, scientists from Johns
Hopkins University, Southwest Research Institute and the Massachusetts
Institute of Technology say they have found two more tiny orbiting satellites,
P1 and P2.
Both are traveling outside the orbit of Charon and are tiny by comparison, the
scientists wrote in the journal Nature.
P1, the more distant of the two from Pluto, has a diameter of between 60 and
165 km while P2 is 20 percent smaller.
"Although definitive orbits cannot be obtained, both new satellites appear
to be moving in circular orbits in the same orbital plane as Charon with
orbital periods of about 38 days for P1 and 25 days for P2," they wrote.
The discovery of the two new members of Pluto's family makes it the only object
in the Kuiper belt—a
vast region of rock and ice beyond Neptune which contains debris from the
formation of the solar system—known to have multiple
satellites, the scientists said.
1. It is implied in the passage that______.
A. Charon was not discovered until the late 1960s
B. Charon is the largest satellite in the solar system
C. all the inner planets are better observed than Pluto
D. Pluto may have some more moons to be discovered
2. The underlined word
"primary" in Paragraph 4 refers to______.
A. size B.
shape C.
planet D. Earth
3. Which of the following show the
possible orbits and positions of Pluto's satellites?
A
B
C
D
4. Which of the following is the
best title for the passage?
A. Pluto: furthest in
the solar system.
B. Pluto: two
additional moons found.
C. Pluto: tiny,
distant and frozen planet.
D. Pluto: two satellites formed in 30 years.