42套数学问题解决——求指教

Olivia_Chenyue

求教Section 1  T5 T7 T13 的答案
5. At a certain diner, a hamburger and coleslaw cost $3.59, and a hamburger and french fries cost $4.40. If french fries cost twice as much as coleslaw, how much do french fries cost?
(A) $0.30 (B) $0.45 (C) $0.60 D) $0.75 (E) $0.90
7. （a/b)/c  In the expression above, a, b, and c are different numbers and each is one of the numbers 2, 3, or 5. What is the least possible value of the expression?
(A)1/30 B)2/15 C) 1/6 (D) 3/10 E) 5/6
13. A certain basketball team that has played 2/3 of its games has a record of 17 wins and 3 losses. What is the greatest number of the remaining games that the team can lose and still win at least 3/4 of all of its games?
(A) 7
(B) 6
(C) 5
(D) 4
(E) 3
T5 coleslaw price X  H+X=3.59  H+2X=4.4   X=0.81  2x=1.62  无选项啊？！ 后面所附的答案为E 0.9...
T7 题目里的式子可以变形为a/bc 吧？abc 各为 2, 3, 5. 代入可以是 2/15， 3/10 , 5/6 .  剩下的1/30 1/6 . 为何答案是B 2/15 ?
T13 all games 30. 至少赢3/4 即 22.5 -17= 5.5 还剩十场 10-5.5=4.5 最大不可以取五吗？
D
请高手指教，谢谢！

ukyo2003

5. At a certain diner, a hamburger and coleslaw cost $3.59, and a hamburger and french fries cost $4.40. If french fries cost twice as much as coleslaw, how much do french fries cost?
(A) $0.30 (B) $0.45 (C) $0.60 D) $0.75 (E) $0.90
这题答案错了吧，这么简单的题没什么弯好绕。我觉得就是1.62

7. （a/b)/c  In the expression above, a, b, and c are different numbers and each is one of the numbers 2, 3, or 5. What is the least possible value of the expression?
(A)1/30 B)2/15 C) 1/6 (D) 3/10 E) 5/6
看你怎么理解least possible value了，公式就是a/bc，所有possible values分别是：2/15, 3/10, 5/ 6其他都不是possible value，所以三个里面最小的是2/15了。

13. A certain basketball team that has played 2/3 of its games has a record of 17 wins and 3 losses. What is the greatest number of the remaining games that the team can lose and still win at least 3/4 of all of its games?
(A) 7
(B) 6
(C) 5
(D) 4
(E) 3
一共30场，超过4/3赢的话至少要赢23 (>22.25的最小整数)场，一共只能输7场，减去已经输的3场，剩下只能输4场。。。

Olivia_Chenyue

ukyo2003 发表于 2015-4-26 12:42
5. At a certain diner, a hamburger and coleslaw cost $3.59, and a hamburger and french fries cost $4 ...

十分感谢！还有两道请指教。
8. A certain culture of bacteria quadruples every hour. If a container with these bacteria was half full at 10:00 a.m., at what time was it one-eighth full?
(A) 9:00 a.m.
9. Al, Lew, and Karen pooled their funds to buy a gift for a friend. Al contributed $2
less than 1/3 of the cost of the gift and Lew contributed $2 more than 1/4 of the cost. If
Karen contributed the remaining $15, what was the cost of the gift?
(A) $24
(B) $33
(C) $36
(D) $43
(E) $45

Olivia_Chenyue

16. There were 36.000 hardback copies of a certain novel sold before the paperback version was issued. From the time the
first paperback copy was sold until the last copy of the novel was sold. 9 times as many paperback copies as hardback
copies were sold. If a total of 441.000 copies of the novel were sold in all, how many paperback copies were sold?
(A) 45.000
(B) 360.000
(C) 364.500
(D) 392.000
(E) 396.900
C
paperback copies  X    X+9x+36000=441000 x=40500 ?

Olivia_Chenyue

17. The figure above shows the dimensions of a rectangular box (长20inches, 宽8 in 高 2 in)  that is to be completely wrapped with paper. If a single sheet of paper is to be used without patching, then the dimensions of the paper could be
(A) 17 in by 25 in
(B) 21 in by 24 in
(C) 24 in by 12 in
(D) 24 in by 14 in
(E) 26 in by 14 in
B  
19. If M and N are positive integers that have remainders of 1 and 3, respectively, when divided by 6, which of the following could NOT be a possible value of M+N?
(A) 86
(B) 52
(C) 34
(D) 28
(E) 10
A
应该选E吧？
M=6x+1 N=6y+3 M+N=6(x+y)+4 所有选项-4后要能被6整除， A x+y=12 E x+y=1 M and N are positive integers...