13. If Sara's age is exactly twice Bill's age, what is Sara's age?
(1) Four years ago, Sara's age was exactly 3 times Bill's age.
(2) Eight years from now, Sara's age will be exactly 1.5 times Bill's age.
Ans: D , I choose E
set Sara's age as S, set Bill's age as B
(1)=>S=2B , S-4=3B, => S=-8
(2)=>S=2B, S+8=1.5B => S=-32
age is impossibly negative. So both is insuficient.I choose E.
20. Is5^k less than 1,000 ?
(1) 5^(k-1)>3,000
(2) 5^(k-1)=5^k-500
Ans: B , i choose D
from (1)=> 5^k>15,000 => 5^k is not less than 1,000 . (1)is sufficent
so i choose D, did I make any mistakes?
14. If Fran jumps straight up off the floor and lands on her feet T seconds later, her feet will reach a max-imum height of 1.22T2 meters above the floor. On one such jump, was Fran off the floor for less than 1 second ?
(1) On her jump Fran’s feet reached a maximum height of 1 meter above the floor.
(2) On her jump Fran spent more than second ascending.
ans: A
I don't understand the whole question. In fact,i am scared about long sentence,even after I read several times, i still don't what does it say.作者: yvonnezenith 时间: 2003-1-22 11:34
13.(1)=>S=2B , S-4=3（B-4) => S=8
(2)=>S=2B, S+8=1.5(B+8) => S=8
20.agree
14.according to my understanding, the desired answer can be explained as whether T<1.
from (1), i have 1=1.22T2?
doubt.作者: joywzy 时间: 2003-1-22 12:24 标题: to yvonnezenith
13, u are right. I made mistakes.
14,can u explain thhis question in Chinesee? Because i can't understand the whole question.What does it mean?
1。22T2没错吗？作者: joywzy 时间: 2003-1-22 14:59 标题: to yvonnezenith
14. If Fran jumps straight up off the floor and lands on her feet T seconds later, her feet will reach a max-imum height of 1.22T^2 meters above the floor. On one such jump, was Fran off the floor for less than 1 second ?
(1) On her jump Fran’s feet reached a maximum height of 1 meter above the floor.
(2) On her jump Fran spent more than 1/4second ascending.
ans: A
sorry, i miss some figures.
let me try:
set the time of jump off as X, set the time of landing as Y
(1)=> X+Y= T, 1.22T^2=1 => T^2=根号(1/1.22) =>T<1 =>X<1
(2)=> X+Y=T, X>1/4,无法得出X<1,
我做得对吗?作者: tongxun 时间: 2003-1-22 19:11
