Question 733604
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The response from the other tutor shows a typical formal algebraic solution -- which the student certainly should understand.<br>
There are occasions where a quick mental solution is advantageous -- as in a timed competitive exam.<br>
Furthermore, solving the problem informally is good brain exercise.<br>
Going with the current, the boat goes 96 km in 8 hours, so its speed with the current is 96/8 = 12 km/hr.
Going against the current, the boat goes 96 km in 12 hours, so its speed against the current is 96/12 = 8 km/hr.<br>
So ADDing the speed of the current to the speed of the boat gives a speed of 12 km/hr, while SUBTRACTing the speed of the current from the speed of the boat gives a speed of 8 km/hr.<br>
Logical reasoning then tells us that the speed of the boat is halfway between those two speeds, which is 10 km/hr; and that makes the speed of the current 2 km/hr.<br>
ANSWERS: boat speed 10 km/hr; current speed 2 km/hr<br>