Question

A sailor can row a boat 8 km. downstream and return back to starting point in 1 hr 40min.
If the speed of the stream is 2 km/hr, find the speed of the boat in still water.
.Evaluate:
cos70° + cos59° _ & si
2200+ sin270 - 8 sin230°

Answer 1

Answer:

Step-by-step explanation:

As in downstream= x+y is the speed

And in upsstream= x-y is the speed . So 8 km is the total distance to cover on one side so,

8÷{x+2}+8÷{x-2}= 1+40÷60 hour.

By solving we get the equation .

5x^2-48x-20=0

So 5x^2-50x+2x-20=20

5x(x-10)+2(x-10)

(5x+2)(x-10)=0

X=-2÷5,10

As negative cannot be the value so x=10