Bill wanted to try out different water craft. he went 62 miles downstream in a motor boat and 27 miles downstream on a jet ski. his speed on the jet ski was 10 mph faster than in the motor boat. bill spent a total of 4 hours on the water. what was his speed in the motor boat?

Respuesta :

The speed of the bill's motor boat is found as 20 mph.

Explain the relation of speed and time?

  • The speed and time relationship is inverse. Distance / time equals speed.
  • If you keep the distance constant, speed rises as time goes down and falls as it goes up.

Here, we're trying to determine the motorboat's speed.

The speed on the skis would be (x + 10) mph if his motorboat speed is x mph.

There are four hours in all;

Speed = distance/time mathematically.

Skiing time is 27/x+10.

The motorboat time is 62/x.

The result of adding both is 4.

Thus;

27/(x + 10) + 62/x = 4

27(x) + 62(x + 10) = 4(x)(x + 10)

27x + 62x + 620 = 4(x² + 10x)

89x + 620 = 4x² + 40x

4x² -49x-620 = 0

By the quadratic formula;

{-b ± √(b²-4ac)}/2a

In which  a = 4, b = -49 and c = -620

= 49 ± √(-49)² -4(4)(-620)/8

Thus,

49+ 111/8 or 49-111/8

As, speed is not negative.

= (49 + 111)/8

= 20 mph

Thus, the speed of the bill's motor boat is found as 20 mph.

To know more about speed and time, here

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