Two people

Two straight lines cross at right angles. Two people start simultaneously at the point of intersection. John walking at the rate of 4 kph in one road, Jenelyn walking at the rate of 8 kph on the other road. How long will it take for them to be 20√5 km apart

Correct result:

t =  5 h

Solution:

v1=4 km/h v2=8 km/h  s=20 5=20 5 km44.7214 km  v=v12+v22=42+824 5 km/h8.9443 km/h  t=s/v=44.7214/8.9443=5 hv_{1}=4 \ \text{km/h} \ \\ v_{2}=8 \ \text{km/h} \ \\ \ \\ s=20 \cdot \ \sqrt{ 5 }=20 \ \sqrt{ 5 } \ \text{km} \doteq 44.7214 \ \text{km} \ \\ \ \\ v=\sqrt{ v_{1}^2+v_{2}^2 }=\sqrt{ 4^2+8^2 } \doteq 4 \ \sqrt{ 5 } \ \text{km/h} \doteq 8.9443 \ \text{km/h} \ \\ \ \\ t=s/v=44.7214/8.9443=5 \ \text{h}



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Tips to related online calculators
For Basic calculations in analytic geometry is helpful line slope calculator. From coordinates of two points in the plane it calculate slope, normal and parametric line equation(s), slope, directional angle, direction vector, the length of segment, intersections the coordinate axes etc.
Two vectors given by its magnitudes and by included angle can be added by our vector sum calculator.
Do you want to convert velocity (speed) units?
Pythagorean theorem is the base for the right triangle calculator.
See also our trigonometric triangle calculator.

 
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