Mark is 10 years younger than Larry. Larry's age in 8 years will exceed twice Mark's age 3 years ago by 4 years. How old is each now?
Mr. West drove his car from home to Chicago at the rate of 40 mph. and returned at a rate of 45 mph. If his time going exceeded his time returning by 30 minutes, find his time going and his time returning.
Tom, Dick, and Harry weigh 50, 85, and 120 lbs. respectively and use a 12 ft. plank for a teeterboard. Tom sits 5 ft., Dick sits 4 ft., and Harry sits 3 ft. from the fulcrum on the same side. The fulcrum is at the midpoint of the board. How far must a 200-pound friend sit from the fulcrum to balance them?
I would a appreciate the answers, and i will reward the first to answer with a special gift. But you must answer them correctly.
PLEASE HeLP I AM CONFUSED SHOW WORK?
2007-11-26 4:03 pm
回答 (3)
2007-11-26 4:12 pm
✔ 最佳答案
Mark is 10 years younger than Larry: M + 10 = LLarry's age in 8 (L + 8) years will exceed twice Mark's age 3 years ago (2*(M - 3)) by 4 years: (L+8) = 2(M-3) + 4
L = M + 10
L + 8 = 2(M-3) + 4
(M+10) + 8 = 2(M-3) + 4
M + 18 = 2M - 6 + 4
M + 18 = 2M -2
M = 20
L = M + 10 = 30
~~~~~~~~~~~~~~~~~~~~~
d = r*t
r1*t1 = r2*t2
r1 = 40mph, t1 = t2+0.5hours
r2 = 45mph, t2 = t2
40*t1 = 45*t2
40(t2+0.5) = 45Tt2
40t2 + 20 = 45t2
5t2 = 20
t2 = 4 hours
t1 = 4.5 hours
~~~~~~~~~~~~~~~~~~~~~~~~~~
T = 50
D = 85
H = 120
F = m*d
F(T) = 50*5 = 250
F(D) = 85*4 = 340
F(H) = 120*3 = 360
F(T+D+H) = 950
F(200) = 200*d
950 = 200d
d = 950/200
d = 4.75 feet = 4 feet 9 inches
2007-11-26 4:24 pm
let m be Mark age now
let y be Larry age now
m=y-10
y+8-2(m-3)=4
solve for m and y
y+8-2y+26=4
-y=-30
y=30
Larry=34,mark=20
let x be the distance
x/40-x/45=.5
45x-40x=900
5x=900
x=180
total time =180/40+180/45=8.5hour
5x50=250
4x85=340
3x120=360
together=950
950/200=4.75ft
let y be Larry age now
m=y-10
y+8-2(m-3)=4
solve for m and y
y+8-2y+26=4
-y=-30
y=30
Larry=34,mark=20
let x be the distance
x/40-x/45=.5
45x-40x=900
5x=900
x=180
total time =180/40+180/45=8.5hour
5x50=250
4x85=340
3x120=360
together=950
950/200=4.75ft
2007-11-26 4:22 pm
l=m+10
L+8 = 2(m-3)+4
m+10+8 = 2(m-3)+4
m=20 l=30
where m = mark l = larry
-----------------
x=to y=return
40x=45y
x=y+0.5
==>40(y+0.5)=45y
y=4hour
x=4.5hour
..........................
i dont work with english units... I will assume lb is the same as pound , otherwise.. make relevant conversions
50*5+85*4+120*3 = 200*length
length = 4.75ft
L+8 = 2(m-3)+4
m+10+8 = 2(m-3)+4
m=20 l=30
where m = mark l = larry
-----------------
x=to y=return
40x=45y
x=y+0.5
==>40(y+0.5)=45y
y=4hour
x=4.5hour
..........................
i dont work with english units... I will assume lb is the same as pound , otherwise.. make relevant conversions
50*5+85*4+120*3 = 200*length
length = 4.75ft
收錄日期: 2021-05-03 12:24:45
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20071126080342AAJujCI