Which of the following shows the prefixes in order from largest to smallest? centi, deci, nano

Deci, Centi, then Nano is the correct order from largest to smallest

Let her initial velocity be U.

Let the width of the river be W.

She swims 3/5 the width of the river  at  U.

Remainder width =  (1 - 3/5) = 2/5.

She then swims 2/5 the width with velocity  U/2.

Average Speed  =  (Total Distance Traveled)  /  ( Total Time Taken).

Distance =  Speed * time

time  =  Distance /  Speed.

Time in first trip:    =    (3/5)W / U =   0.6W/U.

Time in second trip  =  (2/5)W / (U/2)  =  0.4W / 0.5 U =  0.8W/U

Total Distance Traveled =  W,  width of the river.

Average Speed  =      W  /  (0.6W/U  +  0.8W/U) =    W /  (1.4W/U)

                             =  W  *  U / 1.4W 
                              =    U/1.4
                              =  U * 10 / 14
                              =  (5/7) U.

Therefore Average speed is  (5/7) of the initial speed.