# boat speed

• Jul 31st 2010, 09:53 PM
aeroflix
boat speed
a boat is trying to cross a 8km wide lake. the speed of the boat in the first 2 kilometers is unknown but it started to raise it speed 0.5 kilometers per hour faster than the first 2 kilometers. it arrived 10 minutes earlier than expected. find the original speed of the boat.
• Jul 31st 2010, 10:40 PM
CaptainBlack
Quote:

Originally Posted by aeroflix
a boat is trying to cross a 8km wide lake. the speed of the boat in the first 2 kilometers is unknown but it started to raise it speed 0.5 kilometers per hour faster than the first 2 kilometers. it arrived 10 minutes earlier than expected. find the original speed of the boat.

Does this mean that the speed on the last 6km was 1/2 kph greater than on the first 2km?

Let the initial speed be \$\displaystyle \$\$ x\$ kph. Then it would have taken \$\displaystyle 8/x\$ hours to cross the lake at that speed. It in fact took \$\displaystyle [2/x] + [6/(x+0.5)]\$ hours to cross the lake.

Now can you finish?