A boat takes twice as long to travel 5 km upstream as it does travel 3km downstream in a river that flows at a rate of 2 kph. At what speed does the boat travel in still water?

22 kph

Step-by-step explanation:

distance (d) = rate (r) x time (t)

UPSTREAM: d = 5 km,   r = *x - y,  y = 2 kph,   t = 2t

DOWNSTREAM: d = 3 k,  r = *x + y,   y = 2 kph,   t = t

*x is the speed in still water and y is the current of the water.

Upstream equation:       5 = 2t(x - 2)   -->    

Downstream equation:  3 = t(x + 2)     -->    

Set the equations equal to each other to solve for x:

walter needs to make at least 5 more cookies but no more than 40. 5 ≤ x ≤ 40

step-by-step explanation:

20 ≤ x + 15 ≤ 55

subtract 15 from all parts

20-15 ≤ x + 15-15 ≤ 55-15

5 ≤ x ≤ 40

this means how many more cookies he has to make

walter needs to make at least 5 more cookies, but no more than 40 cookies; 5 ≤ x ≤ 40

true !

step-by-step explanation: