Question

a Boat travel 210 km downstream and back. the trip downstream took 10 hours. the trip back took 70 hours what is the speed of boat in still water?​

Answer 1

Answer:

Boat speed =x mph

current speed =y mph

against current x-y 70.00 hours

With current x+ y 10.00 hours

Distance = same= 210 miles

t=d/r

210 / ( x - y )= 70.00

70 ( x - y ) = 210.00

70 x -70 y = 210 .1

210 / ( x + y )= 10.00

10.00 ( x + y ) = 210

10.00 x + 10.00 y = 210 .2

Multiply (1) by 1.00

Multiply (2) by 7.00

we get

70 x + -70 y = 210

70 x + 70 y = 1470

140 x = 1680

/ 140

x = 12 mph

plug value of x in (1)

70 x -70 y = 210

840 -70 y = 210

-70 y = 210 -840

-70 y = -630

y = 9 mph

Step-by-step explanation: