Let x be rate of boat in still water
let y be rate of current
we use this equation to relate quantities:
distance = speed · time
we have two unknowns so we might need to create a system of equationss
upstream:
speed (in km/h) = x - y
(we get speed of boat then subtract the current's speed from it since current is going against boat direction)
time = 3 hours
distance = 144 km
downstream:
speed (in hm/h) = x + y
(we get speed of boat then add the current's spd from it since current is going against boat direction)
time = 2 hours
distance = 144 km (same distance upstream and downstream)
using distance = speed times time
for upstream
144 = 3(x-y)
144 = 3x - 3y
for downstream
144 = 2(x+y)
72 = x + y
system of eqns:
144 = 3x - 3y
72 = x + y
solve by substitution: move 72 = x + y into x = 72 - y and subst into other equation for x
144 = 3(72 - y) - 3y
144 = 216 - 3y - 3y
144 = 216 - 6y
144 - 216 = -6y
-72 = -6y
y = 12 km/h
Use x = 72 - y to find x with y = 12: x = 72 - 12 = 60 km/h
rate of boat in still water is 60 km/h
rate of the current is 12 km/h
Answer:x=0.089
Step-by-step explanation:
C. we multiply the equation by 3
Answer:
I
Step-by-step explanation:
I don't know
Answer:
Average speed
= 5 5/6 mph , or
= 5.83 mph (to 2 decimals)
Step-by-step explanation:
Average speed is total distance divided by the total time it takes to cover the given distance.
Since uphill = 5 mph, and downhill = 7 mph, we know the average speed is between 5 and 7 mph.
Let
x = distance uphill, and also distance downhill.
Total distance = 2x miles
Total time = x/5 + x/7 hours = 12x/35 hours
Average speed
= total distance/total time
= 2x / (12x/35) mph
= 70x / 12x
= 5 5/6 mph
= 5.83 mph (to 2 decimals)
