Common Core: High School - Number and Quantity : Compute Magnitude and Direction of a Scalar Multiple: CCSS.Math.Content.HSN-VM.B.5b

Study concepts, example questions & explanations for Common Core: High School - Number and Quantity

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All Common Core: High School - Number and Quantity Resources

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Example Questions

Example Question #191 : High School: Number And Quantity

Calculate \displaystyle \left \| -10v\right \|, where \displaystyle v=< -6,7>. Also determine the direction of the resulting vector.

Possible Answers:


\displaystyle \left \| -10\:v\right \|=-\sqrt{85}, Direction is away from \displaystyle v.

\displaystyle \left \| -10\:v\right \|=-10\sqrt{85}, Direction is away from \displaystyle v.

\displaystyle \left \| -10\:v\right \|=10\sqrt{85}, Direction is the same as \displaystyle v.

\displaystyle \left \| -10\:v\right \|=10\sqrt{85}, Direction is away from \displaystyle v.

 



\displaystyle \left \| -10\:v\right \|=\sqrt{85}, Direction is the same as \displaystyle v.

Correct answer:

\displaystyle \left \| -10\:v\right \|=10\sqrt{85}, Direction is away from \displaystyle v.

 

Explanation:

In order to solve the first part of the problem, we need to remember how to take the magnitude of a vector and scalar.

\displaystyle \left \| c\:v\right \|=\left | c\right |\:\left \| v\right \|, where \displaystyle c is a scalar.

Now lets calculate this.

\displaystyle \left \| -10\:v\right \|=\left | -10\right |\left \| v\right \|

\displaystyle =10\cdot\sqrt{(-6)^2+7^2}=10\cdot\sqrt{36+49}=10\sqrt{85}

As for the direction of the vector, since \displaystyle c< 0, the resulting vector will be against the original vector \displaystyle v.

See below for a picture.

Screen shot 2016 03 07 at 12.02.14 pm

Example Question #192 : High School: Number And Quantity

Calculate \displaystyle \left \| 7v\right \|, where \displaystyle v=< 8,6>. Also determine the direction of the resulting vector.

Possible Answers:

\displaystyle \left \| 7\:v\right \|=70, Direction is away from \displaystyle v.





\displaystyle \left \| 7\:v\right \|=7, Direction is the same as \displaystyle v.

\displaystyle \left \| 7\:v\right \|=-7, Direction is away from \displaystyle v.

\displaystyle \left \| 7\:v\right \|=-70, Direction is away from \displaystyle v.

\displaystyle \left \| 7\:v\right \|=70, Direction is the same as \displaystyle v.

Correct answer:

\displaystyle \left \| 7\:v\right \|=70, Direction is the same as \displaystyle v.

Explanation:

In order to solve the first part of the problem, we need to remember how to take the magnitude of a vector and scalar.

\displaystyle \left \| c\:v\right \|=\left | c\right |\:\left \| v\right \|, where \displaystyle c is a scalar.

Now lets calculate this.

\displaystyle \left \| 7\:v\right \|=\left | 7\right |\left \| v\right \|

\displaystyle =7\cdot\sqrt{8^2+6^2}=7\cdot\sqrt{64+36}=7\sqrt{100}=7\cdot10=70

As for the direction of the vector, since \displaystyle c>0, the resulting vector will be in the same direction as the original vector \displaystyle v.

See below for a picture.


Screen shot 2016 03 07 at 12.10.09 pm

All Common Core: High School - Number and Quantity Resources

6 Diagnostic Tests 49 Practice Tests Question of the Day Flashcards Learn by Concept
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