伊尔尔吧， 一战结束，遛遛狗

gutou

Cool! Very good memory!
还有这种题啊！有谁可以分享公式啊？加速运动之类的。。。

8. DS： 一个球从斜坡上滚下来，斜坡的长度d与球从坡顶滚到坡地的时间t满足d=t平方。问能否求出球在第一秒内的平均速度和最后一秒内的平均速度之差。
（1）已知坡长25feet
 （2）已知总共用了5s

细细青颜

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lyh76279641

楼主好牛

scauhyl

LZ 大爱

sdcar2010

7.DS：（根号a)*（根号b）=2* 根号下（b+1)，求ab
(1)已知b=一个数
（2）已知a+b=一个数。

Stimulus: ab = 4*(b+1), a>0, b>0.

1) sufficient
2) It depends on the number given since you have to solve an equation to get the value(s) of b.  If only one positive value of b is obtained, then sufficient.  If not, then insufficient.

sdcar2010

8. DS： 一个球从斜坡上滚下来，斜坡的长度d与球从坡顶滚到坡地的时间t满足d=t平方。问能否求出球在第一秒内的平均速度和最后一秒内的平均速度之差。
（1）已知坡长25feet
（2）已知总共用了5s

This is simple.  Both conditions are the same since 25= 5^2.

At the end of the first second, d = 1 ft.  So the v1 average = 1/1 = 1 ft/s
At the end of the 4th second, d = 16 ft.  At the end of the 5th second, d = 25 ft.  So during the last second, the ball covers 25-16 = 9 ft.  So the v5 average = 9/1 = 9 ft/s.

The different between the two is 8 ft/s.

Choose D.

sdcar2010

DS： 一根数轴（有图，大家自己画吧，很容易），上面按顺序从左到右标了XABCDEFGH那么多个点，每点之间间距相等。X对应0，问D是否2的8次方
（1）已知A点是2的6次方
（2）已知B点是2的9次方

From the stimulus, we know that B=2A and D=2B = 4A.

1) D is 2^8. Sufficient.
2) D is not 2^8. Sufficient.

choose D.

sdcar2010

10. DS：一个水缸，往里面加水还是放水忘了，这个没关系……注水速度是均匀的，问注满缸的65%需要多长时间，
（1）缸容积2500盎司
（2）注满80%需要16小时52分30秒——数字乱编的，就是一个很准确的数字

1) Insufficient.
2) Sufficient.

sdcar2010

DS： 已知一个群体200人中有人选A课，有人选B课。（还是说两种语言神马的忘了……），问选A课而不选B课的有多少人
（1）两种课都选的人和两种课都不选的人一样多
（2）选A课不选B课的人是选B课不选A课的人的两倍

Since they only provide ratio instead of a value, none of the condition is sufficient, even when you combine them.

Choose E.

sdcar2010

PS，k=m(m+4)(m+5)一定能被以下哪个数整除：3，5，6. 选项就是只有第一个，只有第二个，第一个和第二个这种类型的。我选只能被3整除

The answer is 3 and 6.
Since (m+4) and (m+5) are consecutive numbers.  So one of them is even and contains a factor of 2. In addition, m, m+4, and m+5 contains a factor of 3.  So their product contains factors of 2 and 3.

A variant of this question could add 2 as one of the factors.

The bottom line is that k=m(m+4)(m+5)一定能被 2, 3, and 6 整除