AP EAMCET Engineering 2018 Apr 22 Shift 2 Paper

Let the speed of the motor boat relative to water is V>C . The speed of the motor boat relative to the land is, V−C .
The distance covered by boat is S in

S

V−C

time and the consumption is,
f(v)=kv3.

S

V−C

.
Here, k is constant.
For minimum consumption,
f′(v)=0
kS

(V−C)3V2−V3(1)

(V−C)2

=0
3V3−3V2C−V3=0
2V3−3V2C=0
V=

3C

2