GRE Subject Test: Math : Vectors

Study concepts, example questions & explanations for GRE Subject Test: Math

varsity tutors app store varsity tutors android store

Example Questions

Example Question #363 : Parametric, Polar, And Vector

What is the vector form of \(\displaystyle 5i-2j+9k\)?

Possible Answers:

\(\displaystyle \left \langle 5,9,-2\right \rangle\)

None of the above

\(\displaystyle \left \langle 9,-2,5\right \rangle\)

\(\displaystyle \left \langle -2,5,9\right \rangle\)

\(\displaystyle \left \langle 5,-2,9\right \rangle\)

Correct answer:

\(\displaystyle \left \langle 5,-2,9\right \rangle\)

Explanation:

Given \(\displaystyle 5i-2j+9k\), we need to map the \(\displaystyle i\)\(\displaystyle j\), and \(\displaystyle k\) coefficients back to their corresponding \(\displaystyle x\)\(\displaystyle y\), and \(\displaystyle z\)-coordinates.

Thus the vector form of \(\displaystyle 5i-2j+9k\) is 

\(\displaystyle \left \langle 5,-2,9\right \rangle\).

Example Question #21 : Vectors

What is the vector form of \(\displaystyle 2i-k\)?

Possible Answers:

None of the above

\(\displaystyle \left \langle 2,-1, 0\right \rangle\)

\(\displaystyle \left \langle 0,-1,2\right \rangle\)

\(\displaystyle \left \langle 2,0,-1\right \rangle\)

\(\displaystyle \left \langle -1,2, 0\right \rangle\)

Correct answer:

\(\displaystyle \left \langle 2,0,-1\right \rangle\)

Explanation:

Given \(\displaystyle 2i-k\), we need to map the \(\displaystyle i\)\(\displaystyle j\), and \(\displaystyle k\) coefficients back to their corresponding \(\displaystyle x\)\(\displaystyle y\), and \(\displaystyle z\)-coordinates.

Thus the vector form of \(\displaystyle 2i-k\) is 

\(\displaystyle \left \langle 2,0,-1\right \rangle\).

Example Question #11 : Vector Form

What is the dot product of \(\displaystyle a=\left \langle 7,-7,0\right \rangle\) and \(\displaystyle b=\left \langle 2, -1,8\right \rangle\)?

Possible Answers:

\(\displaystyle 14\)

\(\displaystyle 7\)

\(\displaystyle -14\)

\(\displaystyle 21\)

\(\displaystyle -21\)

Correct answer:

\(\displaystyle 21\)

Explanation:

The dot product of two vectors is the sum of the products of the vectors' corresponding elements. Given \(\displaystyle a=\left \langle 7,-7,0\right \rangle\) and \(\displaystyle b=\left \langle 2, -1,8\right \rangle\), then:

\(\displaystyle \left \langle 7,-7,0\right \rangle\times \left \langle 2, -1,8\right \rangle\)

\(\displaystyle =(7\times 2)+(-7\times -1)+(0\times 2)\)

\(\displaystyle =14+7+0\)

\(\displaystyle =21\) 

Example Question #21 : Vector Form

What is the dot product of \(\displaystyle a=\left \langle 4,1,-1\right \rangle\) and \(\displaystyle b=\left \langle 2, -1,8\right \rangle\)?

Possible Answers:

\(\displaystyle 17\)

\(\displaystyle 16\)

\(\displaystyle -1\)

\(\displaystyle 1\)

\(\displaystyle -8\)

Correct answer:

\(\displaystyle -1\)

Explanation:

The dot product of two vectors is the sum of the products of the vectors' corresponding elements. Given \(\displaystyle a=\left \langle 4,1,-1\right \rangle\) and \(\displaystyle b=\left \langle 2, -1,8\right \rangle\), then:

\(\displaystyle \left \langle 4,1,-1\right \rangle\times \left \langle 2, -1,8\right \rangle\)

\(\displaystyle =(4\times 2)+(1\times -1)+(-1\times 8)\)

\(\displaystyle =8+(-1)+(-8)\)

\(\displaystyle =-1\) 

Example Question #25 : Vectors

What is the dot product of \(\displaystyle a=\left \langle 3,0,-9\right \rangle\) and \(\displaystyle b=\left \langle -9, 2,-3\right \rangle\)?

Possible Answers:

\(\displaystyle -27\)

\(\displaystyle 9\)

\(\displaystyle 0\)

\(\displaystyle 27\)

\(\displaystyle -9\)

Correct answer:

\(\displaystyle 0\)

Explanation:

The dot product of two vectors is the sum of the products of the vectors' corresponding elements. Given \(\displaystyle a=\left \langle 3,0,-9\right \rangle\) and \(\displaystyle b=\left \langle -9, 2,-3\right \rangle\), then:

\(\displaystyle \left \langle 3,0,-9\right \rangle\times \left \langle -9, 2,-3\right \rangle\)

\(\displaystyle =(3\times -9)+(0\times 2)+(-9\times -3)\)

\(\displaystyle =(-27)+0+27\)

\(\displaystyle =0\) 

Example Question #403 : Gre Subject Test: Math

What is the vector form of \(\displaystyle a=\left \langle 3,-2,7\right \rangle\)?

Possible Answers:

\(\displaystyle 3i-2j+7k\)

\(\displaystyle -3i-2j-7k\)

\(\displaystyle 3i+2j-7k\)

\(\displaystyle 3i+2j+7k\)

\(\displaystyle 3i-2j-7k\)

Correct answer:

\(\displaystyle 3i-2j+7k\)

Explanation:

In order to derive the vector form, we must map the \(\displaystyle x\)\(\displaystyle y\)\(\displaystyle z\)-coordinates to their corresponding \(\displaystyle i\)\(\displaystyle j\), and \(\displaystyle k\) coefficients.

That is, given \(\displaystyle a=\left \langle a_{1},a_{2},a_{3}\right \rangle\), the vector form is \(\displaystyle a_{1}i+a_{2}j+a_{3}k\).

So for \(\displaystyle a=\left \langle 3,-2,7\right \rangle\), we can derive the vector form \(\displaystyle 3i-2j+7k\).

Example Question #21 : Vectors

What is the vector form of \(\displaystyle a=\left \langle -1,9,3\right \rangle\)?

Possible Answers:

\(\displaystyle i+9j+3k\)

\(\displaystyle -i-9j-3k\)

\(\displaystyle -i+9j+3k\)

\(\displaystyle -i-9j+3k\)

\(\displaystyle i-9j+3k\)

Correct answer:

\(\displaystyle -i+9j+3k\)

Explanation:

In order to derive the vector form, we must map the \(\displaystyle x\)\(\displaystyle y\)\(\displaystyle z\)-coordinates to their corresponding \(\displaystyle i\)\(\displaystyle j\), and \(\displaystyle k\) coefficients.

That is, given \(\displaystyle a=\left \langle a_{1},a_{2},a_{3}\right \rangle\), the vector form is \(\displaystyle a_{1}i+a_{2}j+a_{3}k\).

So for \(\displaystyle a=\left \langle -1,9,3\right \rangle\), we can derive the vector form \(\displaystyle -i+9j+3k\).

Example Question #22 : Vector

What is the vector form of \(\displaystyle a=\left \langle 0,2,5\right \rangle\)?

Possible Answers:

\(\displaystyle 2j+5k\)

None of the above

\(\displaystyle 5i+2j\)

\(\displaystyle 2i+5j\)

\(\displaystyle 2i+5k\)

Correct answer:

\(\displaystyle 2j+5k\)

Explanation:

In order to derive the vector form, we must map the \(\displaystyle x\)\(\displaystyle y\)\(\displaystyle z\)-coordinates to their corresponding \(\displaystyle i\)\(\displaystyle j\), and \(\displaystyle k\) coefficients.

That is, given \(\displaystyle a=\left \langle a_{1},a_{2},a_{3}\right \rangle\), the vector form is \(\displaystyle a_{1}i+a_{2}j+a_{3}k\).

So for \(\displaystyle a=\left \langle 0,2,5\right \rangle\), we can derive the vector form \(\displaystyle 2j+5k\).

Example Question #29 : Vectors

What is the vector form of \(\displaystyle 5i-6j+7k\)?

Possible Answers:

\(\displaystyle \left \langle 5,6,7\right \rangle\)

\(\displaystyle \left \langle -5,-6,-7\right \rangle\)

\(\displaystyle \left \langle 5,6,-7\right \rangle\)

\(\displaystyle \left \langle 5,-6,7\right \rangle\)

\(\displaystyle \left \langle 5,-6,-7\right \rangle\)

Correct answer:

\(\displaystyle \left \langle 5,-6,7\right \rangle\)

Explanation:

In order to derive the vector form, we must map the vector elements to their corresponding , , and coefficients. That is, given, the vector form is  . So for \(\displaystyle 5i-6j+7k\), we can derive the vector form \(\displaystyle \left \langle 5,-6,7\right \rangle\).

Example Question #221 : Algebra

What is the vector form of \(\displaystyle -2i+9j\)?

Possible Answers:

\(\displaystyle \left \langle9, 0,-2\right \rangle\)

None of the above

\(\displaystyle \left \langle -2,9,0\right \rangle\)

\(\displaystyle \left \langle 0,-2,9\right \rangle\)

\(\displaystyle \left \langle-2, 0, 9\right \rangle\)

Correct answer:

\(\displaystyle \left \langle -2,9,0\right \rangle\)

Explanation:

In order to derive the vector form, we must map the vector elements to their corresponding , and coefficients. That is, given , the vector form is  . So for \(\displaystyle -2i+9j\), we can derive the vector form \(\displaystyle \left \langle -2,9,0\right \rangle\).

Learning Tools by Varsity Tutors