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甲乙两台机器，它们的功率之比为3：1．当它们做相同的功时，所用时间之比为：______，在相同时间内完成的功之比为：______．

答案

∵甲乙两台机器的功率之比为：3：1，

∴它们做相等的功所用时间之比为：

t甲
t乙
=
W
P甲
W
P乙
=
P乙
P甲
=
1
3
，

它们在相同时间内所做功之比为：

W甲
W乙
=
P甲t 
P乙t
=
P甲
P乙
=
3
1
．

故答案为：1：3；3：1．

多项选择题

保险产品理财产品包括以下产品( )。

A．金融期货

B．金融期权

C．人身保险

D．财产保险

E．投资理财类保险
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阅读理解
阅读理解。
     Vans, Keds, Dollies-they sound like the names of rock bands, but if you have teenagers, you'll know they're
actually the latest in teenage footwear.
     But experts are now warning that the current shoe fashions will be causing teenagers discomfort in the short
term and storing up years of foot, knee and back pain in the future.
     Here, the experts identify the problems caused by teenagers' shoe choice.
KEDS/VANS
     Slip-on shoes with elastic (弹性的) sides are particularly popular among teenage boys-
with Keds and Vans the most sought-after brands.
     The main problem is that they are just too flat-so flat that the heel, which strikes the
ground first, also becomes damaged and painful.
BALLET PUMPS
     The worst shoes of all are such light and thin dolly shoes. The problem is partly their
flatness, as with Keds and Vans. However ballet pumps, which have no string or heel, have
other specific problems.
     "As the shoe has no fastening device, it relies on the toes to keep the shoe on, causing an
awkward gait (步法), this leads to short- and long-term problems such as calluses (茧子),
heel and knee pain."
WEDGES AND STILETTOS
     These shoes can also cause problems with gait. They may look good, but the heels on
these are so high they can force the wearer's body weight forward, making them very
unstable.
     Teens who wear these shoes regularly are also in danger of joining those millions of
women with constant back pain.
SCHOOL SHOES
     So what do podiatrists (足科医生) have on their wish list, especially for everyday wear?
     Something in a natural, breathable fabric, with a string to hold it on, with a small heel and a deep toe-box that
does not press the toes, such as Clark's, Marks & Spencer or Rhino.
     If your teen insists on wearing 'bad' shoes, get them some simple foot orthotics (矫形器) in the shoes. These
support and correct the movement of the foot and, properly fitted by a podiatrist, can often transform their walk
and halt the damage.
1. Of all the shoes mentioned in the passage, which can cause the worst problems?
A. Marks & Spencer.
B. Wedges & Stilettos.
C. Keds and Vans.
D. Ballet Pumps.
2. Which pair of shoes may not be found on the podiatrists' wish list?
A.  B.  C.  D.
3. The underlined word "halt" in the last paragraph probably means _____.
A. increase
B. worsen
C. stop
D. cure
4. From this passage we can infer _____.
A. trendy shoes may ruin teenagers' health
B. fashionable shoes all have orthotics in them
C. experts are strongly against wearing popular shoes
D. podiatrists are expert at producing branded shoes
5. In which column of Mail Online can you find this passage?
A. Sports.
B. Science.
C. Health.
D. Shopping.
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