Answer:
Speed of the boat is 9.4mph and the current is 15.4mph
Explanation:
Rate= distance/ time
With current; rate= boat+ current= b+c
Against current; rate= boat - current = b- c
30=3(b+c)••••••••••••••eqn(1)
30=5(b-c)•••••••••••••••••eqn(2)
30=3b +3c••••••••••••••eqn(3)
30=5b-5c•••••••••••••••eqn(4)
Solve simultaneously
b=12mph
From eqn(3)
30=3b +3c
Divide both sides by 3, we have
10= b+c
If we make "b" the subject of the formula we have
b= (10-c)••••••••eqn(5)
Divide both side of eqn(4) by 5 we have
6=b-c••••••••eqn(7)
Substitute eqn(5) into 7
6= (10-c)-c
6= 10c-c^2
C^2-10c+6
C= 9.4 or 0.64
Substitute the highest value 9.4 into equation 7
6=b-9.4
b=6+9.4
b= 15.4
Speed of the boat is 9.4mph and the current is 15.4mph