It takes a boat 3 hours to travel 30 miles down a river and 5 hours to return upstream to its starting point. What is the rate of the current in the river? for this I got X=8 and Y=2 but I dont know how to find the rate of the current river!
A videocassette manufacturer has determined that its weekly cost equation is C = 3000 + 11x, where x is the number of cassettes produced and sold each week. If the cassettes are sold for $16 to distributors, how many must be sold each week for the manufacturer to break even? I have no clue on how to do this one at all.
2006-09-19 03:09:02 · 4 answers · asked by vikky4all2006 1 in Education & Reference ➔ Homework Help
1.) It takes a boat 3 hours to travel 30 miles down a river and 5 hours to return upstream to its starting point. What is the rate of the current in the river?
Assume the boat has a constant speed:
vb = b + r
vb = velocity of the boat = boat's speed + river's flow rate
vbd = 10mi/hr (30/3)
vbu = 6 mi/hr (30/5)
If the boat and the river have constant speeds, then the average rate will be the boat's speed, and the difference between the extremes and the average will be the river's speed:
Average vb = vbd + vbu / 2 = 16/2 = 8 mi/hr (boat's speed)
Extreme - average = 10 - 8 = 2 mi/hr (river's rate)
2.) A videocassette manufacturer has determined that its weekly cost equation is C = 3000 + 11x, where x is the number of cassettes produced and sold each week. If the cassettes are sold for $16 to distributors, how many must be sold each week for the manufacturer to break even?
Cost = 3000 + 11x, because there is an initial cost of $3000, and it costs 11 per cassette.
The break even point is where the Revenue = Cost, where Revenue = 16x
So:
16x = 3000 + 11x
5x = 3000
x = 600 cassettes
2006-09-19 03:16:26 · answer #1 · answered by ³√carthagebrujah 6 · 0⤊ 0⤋
The average speed down the river was 10mph. The average speed up the river was 6mph. Assuming the boat's speed was the same for both trips, B+C=10 and B-C=6
add the two equations: 2B=16 B=8 so Current = 2mph
2006-09-19 10:28:17 · answer #2 · answered by davidosterberg1 6 · 0⤊ 0⤋
It feels like there is information missing from that second problem... you sure you have everything captured here?
2006-09-19 10:20:17 · answer #3 · answered by Anonymous · 0⤊ 0⤋
to down boat+current
to up boat-current
3(b+c)=30
5(b-c)=30
or
b+c=10
b-c=6
by addition
2b=16
b=8
c=2
You are right.
2006-09-19 10:16:49 · answer #4 · answered by iyiogrenci 6 · 0⤊ 0⤋