Question

21. The speed of a boat in still water is x km/hr and the speed of the stream is 3 km/hr.
(i) Write the speed of the boat upstream, in terms of x.
(ii) Write the speed of the boat downstream, in terms of x.
(iii) If the boat goes 15 km upstream and 22 km downstream in 5 hours, write an equation in x to represent the statement.
(iv) Solve the equation to evaluate x.
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Answer 1

Step-by-step explanation:

let X be the speed of boat

in upstream 1/X-15...............1

indown stream 1/X+22.........2

from 1 and 2

1/x-15+1/X+22=5houres

(X+22)+x-15/(x-15)(X+22=5

2x+7/x^2-(7)^2=5

2x+7/x^2-49=5

5(x^2-49)=2x+7

5x^2-245=2x+7

5x^2-238=2x

5x^2-2x-238=0

X=-b-or+✓b^2-4ac/2a

=2+-✓{2}^2-4×5×-238/2×5

2+-✓4-(-4760)/10

2+-✓4+4760/10

2+-✓4764/10

2+-69/10

2+69/10and2-69/10

X=7.1