Question

A boat makes a 120-mile trip downstream in 3 hours but makes the return trip in 4 hours. What is the rate of the current?

answer list
3 mph
4 mph
5 mph

Answer 1

do u know how to do this

Answer 2

using algebra
Let ‘c’ be the rate of current,
and ‘b’ be the rate of boat with no current...

Answer 3

ok

Answer 4

remember,
distance = rate \(\times\) time
\(\large D=r \cdot t\) .... or

\[\implies \Large \frac D r = t\]

Answer 5

40

Answer 6

so, you get 2 equations:
\[\Large {120 \over 3} = b+c\]

\[\Large {120 \over 4} = b-c\]

solve for c

Answer 7

how do i do that

Answer 8

have you used simultaneous equations before?

Answer 9

did you understand how to get the two equations above?

Answer 10

1 one is 40b+c an the 2 one is 30=b-c an no

Answer 11

yea, so to get ‘c’, we subtract the second equation from the first

Answer 12

how does this look like

Answer 13

\[\large 40 = b+c\]\[\large 30 = b-c\]- - +\[\large \overline{10 = 0+2c}\]

Answer 14

5=c

Answer 15

\[\Huge \checkmark\]

Answer 16

yes thx alot

Answer 17

if you wanted to know the speed of the boat b:
plug in 5 for c in any 1 of the 2 equations
...........you get 35