ok i know how to solve these and ive done it before but for some reason i cant get this one:
In 30 minutes Bobby can row 290 fathoms with the current. Against the current it takes 45 minutes to row 150 fathoms. Find his rate and the water current.
2007-12-06 11:54:45 · 12 answers · asked by Ivy 4 in Education & Reference ➔ Homework Help
figure out the rate for the first then compare:
D= r x t
1. 290 fathoms = (bob rate + current rate) x 30 minutes
2. 150 fathoms = (bob rate - current rate) x 45 minutes
Now you can solve these with simple addition of equations and substitutions.
(bob rate + current rate) = 290/30 = 9 2/3 fathoms /minute
(bob rate - current rate) = 150/45 = 3 1/3 fahoms / minute
2 bob rates = 13 fathoms / minute
bob's rate = 6 1/2 fathoms/ minute
6.5 + current rate = 9 2/3
current rate = 3 1/6 fathoms/minute
2007-12-06 11:57:20 · answer #1 · answered by ignoramus 7 · 0⤊ 0⤋
If you want the rates in per/hour units, change the 30 min to 0.5 hr and 45 min to 0.75 hr
Distance = time times rate
So 290 = 0.5(r+c)
and 150 = 0.75(r - c) [r = rate; c = current]
Solve those
Hint: multiply first by 6 and second by 4 getting
1740 = 3(r+c)
600 = 3(r-c)
then multiply out then add the two rows
2007-12-06 12:01:57 · answer #2 · answered by hayharbr 7 · 0⤊ 0⤋
Let X = Bobby's Rate and Y Be the Current Rate
Solve:
30X + 30Y = 290 --> 90X + 90Y = 870
45X - 45Y = 150 --> 90X - 90Y = 300
--> 180 X = 1170
X=6.5
Y =3.16667
2007-12-06 11:59:27 · answer #3 · answered by Daniel L 2 · 0⤊ 0⤋
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2016-12-17 09:45:21 · answer #4 · answered by ? 4 · 0⤊ 0⤋
you have to find the rate of change. the equation is [y=kx] 290 is the y, uhh I'm in algebra I hate it, and I can't think right now. Good Luck!
2007-12-06 11:58:42 · answer #5 · answered by catiecat 3 · 0⤊ 0⤋
just find the rate for each one (distance divided by time) and then subtract the two
2007-12-06 11:58:21 · answer #6 · answered by Jaquline 3 · 0⤊ 0⤋
omigosh, I am in algebra two and cannot figure that out, it just don't really make since! I am sooo sorry!
2007-12-06 11:59:27 · answer #7 · answered by countrygirl 1 · 0⤊ 0⤋
algebra 1. i don't remember this off the top of my head...go to the textbook website it should have something to help u...i hope!
2007-12-06 11:57:51 · answer #8 · answered by Anonymous · 0⤊ 0⤋
cross multiply it. a proportion or something. then the rate
2007-12-06 11:58:33 · answer #9 · answered by Anonymous · 0⤊ 0⤋
It's a ratio fomula.
2007-12-06 11:57:38 · answer #10 · answered by stale mate 3 · 0⤊ 0⤋