Please help me && explain how you got this answer : /
When she rows with the current, Mindy can row 24 miles in 3 hours. Against the same current, Mindy can row only 2/3 of this distance in 4 hours. Find the rate of the current and Mindy’s rowing rate in still water. Assume that both rates are constant.
This problem is driving me crazy!!! Because they game me this:
Note: For a boat traveling in a stream, current has an affect similar to that of wind on an aircraft. A boat traveling upstream is traveling against the current. A boat traveling downstream is traveling with the current.
And that so called “hint” is frustrating because all it was was common sense.
So I discovered this:
Downstream ….Speed = rowing rate + current
Upstream….Speed = rowing rate - current
So rate x time = distance
(r+c) ....3 ....24
(r-c) ....4 ....2/3(24)
Now please help me figure out the rest. This problem is giving me a headache
2006-12-07 02:56:00 · 4 answers · asked by xolifes2sh0rtox 1 in Science & Mathematics ➔ Mathematics
First lets find the 2/3 of the distance against the stream
24* 2/3= 16 miles
Now let's convert everything to miles per hr
24mi/ 3hrs = 8 mi/hr
16mi/ 4hrs= 4mi/hr
R +C= 8mi/hr
R - C= 4 mi/hr
add two eqn
2R= 12mi/hr
divide by 2
R= 6mi/hr
Rate of current is
R+ C= 8mi/hr
6 + C= 8mi/hr
C= 2mi/hr
At still water Mindy can travel at 6 mi/hr
so in 4hrs Mindy will travel 6*4= 24miles
2006-12-07 03:05:00 · answer #1 · answered by ۞ JønaŦhan ۞ 7 · 4⤊ 0⤋
You've already done the hard part ☺
(r + c)*3 = 3r + 3c = 24
(r - c)*4 = 4r - 4c = (2/3)*24 = 16
so factor out the 3 from the 1'st equation and the 4 from the 2'nd to get
r + c = 8
r - c = 4
add the equations together to get
2r = 12 => r = 6
substitute this value back into the first equation and solve it for c (you should get 2) and you're done.
Doug
2006-12-07 03:12:56 · answer #2 · answered by doug_donaghue 7 · 0⤊ 0⤋
from where you left off
3(r+c) = 24 so r+c = 8
4(r-c) = 16 so r-c = 4 , so r = c+4
sub into eqn 1
c+4 + c = 8
2c = 4
c=2
thus
r = 2 + 4
r = 6
2006-12-07 03:06:22 · answer #3 · answered by alia_vahed 3 · 0⤊ 0⤋
8=rowing rate + current
4=rowing rate - current
_______________________
add them to get this
12=2*rowing rate
rowing rate=6 mph so the current is 2 mph
2006-12-07 03:06:16 · answer #4 · answered by JP 2 · 1⤊ 0⤋