Okay I have the answer - but I don't know how to get to it.... (detailed explanation please - just the basic math on how to solve it.)
If a boat goes downstream 72 miles in 3 hours and upstream 60 miles in 6 hours, the rate of the river and the rate of the boat in still water respectively are ___________?
2006-07-02 07:14:18 · 7 answers · asked by Iram 3 in Science & Mathematics ➔ Mathematics
intel-knight - great job - that's the right answer. My question now is how do you know to add 1o + 24 and / 2 and then subract 1o from the answer? Is there a formula for this or did you somehow figure it?
2006-07-02 07:27:37 · update #1
Lets do by taking equations..it will surely help in understanding.
Let the speed of the boat = x;
Let the speed of the stream = y;
Distance covered in downstream = 72 miles.
Time taken = 3 hrs.
therefore, speed of the boat +stream = 72/3=24 miles/hr.
Distance covered in upstream=60 miles.
Time taken=6 hrs.
Speed=60/6=10 miles/hr
In downstream,
x+y=24;
In upstream,
x-y=10;
hence,
by solvin both equations, we get x=17;
and y=17-10=7
speed of the boat =17 miles/hr.
speed of the stream=7 miles/hr.
Hope the answer matches.
as in the additional ques that u asked...actually in downstream the boat is going wid the flow of the current...so we add both speeds of the boat as well as the current...as in case of upstream...the boat is going opposite that of the current...so as the speed of the boat is more...we subtract the speed of stream from it ,..!! hope dat makes it clear !!
2006-07-02 07:33:54 · answer #1 · answered by Anonymous · 1⤊ 0⤋
Downstream it is 24 mph, upstream it is 10 mph...
half of the difference is the river's speed (cuz in one direction it adds to the boat, in the other it subtracts) 24-10=14... 14/2 is 7...
The river moves 7mph.
so knowing that , 10+7 is 17... double check on the other side... 24-10=17..
the boat is going 17 mph reletive to the water.
2006-07-02 07:26:15 · answer #2 · answered by evalmonk 3 · 0⤊ 0⤋
downstream speed 72/3 = 24 mph
upstream speed 60/6 = 10 mph
boat speed = (10+24)/2 = 17 mph
river speed = 17-10 = 24-17 = 7 mph
which is kinda silly b/c only mountain rivers are that fast, and you can't use speedboats on them.
2006-07-02 07:17:08 · answer #3 · answered by Anonymous · 0⤊ 0⤋
it seems like there is some information missing. perhaps there is a formula that you are supposed to use. based on what is available, you can figure out the speed of the boat, but there doesn't appear to be a means of determining how the river affects the speed of the boat in either direction.
2006-07-02 07:24:44 · answer #4 · answered by Devaughn 1 · 0⤊ 0⤋
Shru gave you the best method to solve the problem. It is a pity though that she chose such a silly nick name
2006-07-02 10:10:27 · answer #5 · answered by Anonymous · 0⤊ 0⤋
unique fee:......M / W = a million / 3. go multiply:......W = 3M....(a million) After boarding: .....................( M + 5 ) / ( W + 5 ) = 2 / 5..........go multiply ...................5( M + 5 ) = 2( W + 5 )..... Simplify ......................5M + 25 = 2W + 10....(2) .... replace equation (a million) in equation (2) ......................5M + 25 = 2( 3M ) + 10 ......................5M + 25 = 6M + 10 . fixing for M ................................M= 15...... (3) Equation (3) in equation (a million) ................................W= 3(15) = 40 5 initially there have been 15 adult males and 40 5 women persons word : Given a share ...A / B = C / D then while we go multiply we get A.D = B.C
2016-12-08 14:59:21 · answer #6 · answered by sherrick 4 · 0⤊ 0⤋
i agree with intel knight
2006-07-02 07:20:28 · answer #7 · answered by Anonymous · 0⤊ 0⤋