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2 years ago

12. A cyclist travels 40 km at a speed of x km/h. Find the time

Mathematics

2 answers:

GREYUIT [131]2 years ago

7 0

Answer:

Step-by-step explanation:

distance = rate times time, so

distance

time = --------------

rate

Here the distance is 40 km and the rate is x. Then

40 km

time = -------------- = (40/x) hr

x km/hr

If the speed is reduced by 2 km/hr, we get:

40 km 40 km 40

time = ------------------------------- or time = ----------------------- = --------- hr

(x km/hr - 2 km/hr) (x - 2) (km/hr) x - 2

The difference between the times is:

40 40

-------- - --------- = 1 hr Solve this for the original speed, x

x - 2 x

40x - 40x + 80 80

----------------------- = 1 hr or ------------ = 1 or 80 = x^2 - 2x

x(x - 2) x(x - 2)

Rewriting this in standard quadratic form: x^2 - 2x - 80 = 0

Here a = 1, b = -2 and c = -80, and so the discriminant b^2 - 4ac is:

(-2)^2 - 4(1)(-80) = 324

The solutions are:

-(-2) ± √324 2 ± 18

x = -------------------- = ------------ = 1 ± 9, or 10 (discard the other root)

2 2

The original speed was 10 km/hr

Ket [755]2 years ago

4 0

the answer is 10 km/hr.

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D = RT would be the fundamental equation to answer this, which is

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It is now.

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What is the formula for rate and distance?

Use the formula d = st to determine speed, distance, or time. Distance is equal to speed multiplied by time. Given two known numbers, the Speed Distance Time Calculator can solve for the unknown sdt value.

Units of seconds (s), minutes (min), hours (hr), or hours, minutes, and seconds can be used to input or solve for time (hh:mm:ss). Time format shortcuts are shown below.

Use the formula d = st, or distance equals speed times time, to find the distance.

Distance Equals speed x time

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Learn more about rate and distance brainly.com/question/1090517

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