Q14:
How many seconds will it take for a car that is traveling at a constant rate of 45 miles per hour to travel a distance of 22 yards? (1 mile = 1,160 yards)
A. 8
B. 9
C. 10
D. 11
E. 12
我怎么答案算出来一个都不对啊!!
Q16:
If n is a positive integer and r is the remainder when (n-1)(n+1) is divided by 24, what is the value of r?
(1) 2 is not a factor of n.
(2) 3 is not a factor of n.
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.
不会做,提供个思路把!
Q31:
一个立方体
In the rectangular solid above, the three sides shown have areas 12, 15, and 20, respectively. What is the volume of the solid?
A. 60
B. 120
C. 450
D. 1,800
E. 3,600
答案为什么是A,我理解有问题?不就是容积啊
14.the answer is wrong.it should be 45*1160=522000/3600=14.5 yards per second;22/14.5==1.52 second
16.learned from statement (1),we know that n is an odd number, therefore, (n-1)(n+1) is a consecutive even number which could be divised by 8;statement (2) indicates that n is an even number,so (n-1)(n+1) is a consecutive odd number which could be divised by 3. So, c is the correct answer.
31.
jj
416 7个连续整数，问有几个是6的倍数。1）中位数是6的倍数。2）和是6的倍数 选D
2)怎么算？
n,n+1, n+2, n+3,n+4,n+5, n+6
相加总共 7n+21 =6k
得出n+3 是6的倍数
所以2和1一样
只有1个
那道楼上说的思路接受不了
你代数进取看看
n^2=24k+r+1
1> 带 5，7，9
2〉同样方法
1+2=> r=1
14.the answer is wrong.it should be 45*1160=522000/3600=14.5 yards per second;22/14.5==1.52 second
16.learned from statement (1),we know that n is an odd number, therefore, (n-1)(n+1) is a consecutive even number which could be divised by 8;statement (2) indicates that n is an even number,so (n-1)(n+1) is a consecutive odd number which could be divised by 3. So, c is the correct answer.
31.
同意
31注意是面积是12,15,20
偶以前模考也是错了
n,n+1, n+2, n+3,n+4,n+5, n+6
相加总共 7n+21 =6k
得出n+3 是6的倍数
所以2和1一样
只有1个
如何的来的阿?
好像是7n+3是6的倍数才对吧?
如何的来的阿?
好像是7n+3是6的倍数才对吧?
三个面的面积是12，15，20。
长方体的边位，x,y,Z
a)xy=12
b)yz=15
c)xz=20
长方体的体积=x*y*z
a*b*c=x^2*y^2*z^2=12*15*20=3600
x*y*z=(a*b*c)^(1/2)=(3600)^(1/2)=60
答案是：A
我知道了，，，刚查了google原来1mile＝ 1760yards 而不是1160
难怪我怎么算也算不出答案来！
Q16:
If n is a positive integer and r is the remainder when (n-1)(n+1) is divided by 24, what is the value of r?
(1) 2 is not a factor of n.
(2) 3 is not a factor of n.
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.
我是这样想的，不知道对不对。。。
(1)n odd 1 3 5 7 9 11
(2)n不是3的倍数 1 2 4 5 7 8 10 11
取交集
n= 1 5 7 11 13 17...
连续正整数，3个数为一组，中间的是n，说明(n-1)、(n+1) 中有一个一定是3的倍数且2个数都是偶数。(n-1)(n+1)=24a+r 一定是24的倍数，r=0。eg:n=5,(n+1)(n-1)=24
Q16:
If n is a positive integer and r is the remainder when (n-1)(n+1) is divided by 24, what is the value of r?
(1) 2 is not a factor of n.
(2) 3 is not a factor of n.
我是这样想的，不知道对不对。。。
(1)n odd 1 3 5 7 9 11
(2)n不是3的倍数 1 2 4 5 7 8 10 11
取交集
n= 1 5 7 11 13 17...
连续正整数，3个数为一组，中间的是n，说明(n-1)、(n+1) 中有一个一定是3的倍数且2个数都是偶数。(n-1)(n+1)=24a+r 一定是24的倍数，r=0。eg:n=5,(n+1)(n-1)=24
对的
不过n＝1 5 7 11 13 17... 这个式子没有规律写不出通项，从这个角度出发怎么推导呢？
可以直接这样想：
连续三个整数中必有一个是3的倍数，由条件2）n不是3的倍数 => （n-1）和（n+1）中一定有一个是3的倍数
条件1）n不是偶数 => （n-1）和（n+1）必均为偶数，且中间有一个是4的倍数 => 2的倍数×4的倍数 =>(n-1)(n+1)必为8的倍数
所以，必为24的倍数
看来14题就是错的
我觉得16题应该选c
最简单的方法---试算
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