In a certain number of hours a woman traveled 6 km. If she had traveled 3 km more per hour, it would have taken her 7 h less to make the journey. How many kilometers did she travel per hour? (Keep three significant digits.

We will define the following variables to solve the problem:

s: normal speed

t: normal time

We write the following system of equations:

6 = s * t

6 = (s + 3) * (t-7)

Rewriting the equation two we have:

6 = s * t - 7s + 3t - 21

Substituting:

s = 6 / t

6 = (6 / t) * t - 7 (6 / t) + 3t - 21

Multiplying both sides by t:

6t = 6t - 42 + 3t ^ 2 - 21t

Rewriting:

3t ^ 2 - 21t - 42 = 0

We take the positive root:

t = 7/2 + root (105) / 2

t = 8.62 h

We look for the value of the speed:

s = 6 / t

s = 6 / 8.62

s = 0.696 km / h

Answer:

she did travel 0.696 kilometers per hour