HSPT Math : HSPT Mathematics

Study concepts, example questions & explanations for HSPT Math

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Example Questions

Example Question #1761 : Hspt Mathematics

Define an operation \(\displaystyle \bigstar\) on the set of real numbers as follows:

\(\displaystyle a \bigstar b = \frac{a+b}{ab}\).

If \(\displaystyle a \bigstar \frac{1}{2} = -1\), evaluate \(\displaystyle a\).

Possible Answers:

\(\displaystyle a = 3\)

\(\displaystyle a = - \frac{1}{3}\)

\(\displaystyle a = \frac{1}{3}\)

\(\displaystyle a = -3\)

Correct answer:

\(\displaystyle a = - \frac{1}{3}\)

Explanation:

\(\displaystyle a \bigstar b = \frac{a+b}{ab}\)

so

\(\displaystyle a \bigstar \frac{1}{2} = \frac{a+ \frac{1}{2} }{a \cdot \frac{1}{2} } = \frac{\frac{2a}{2}+ \frac{1}{2} }{ \frac{a}{2} } = \frac{\frac{2a+1}{2} }{ \frac{a}{2} }\)

Equivalently

\(\displaystyle a \bigstar \frac{1}{2} = \frac{2a+1}{2} \div \frac{a}{2} = \frac{2a+1}{2} \cdot \frac{2}{a} = \frac{2a+1}{a}\)

\(\displaystyle a \bigstar \frac{1}{2} = -1\), so set this equal to \(\displaystyle -1\):

\(\displaystyle \frac{2a+1}{a} = -1\)

\(\displaystyle \frac{2a+1}{a} \cdot a = -1 \cdot a\)

\(\displaystyle 2a+1 = -a\)

\(\displaystyle 2a+1 + a - 1 = -a + a - 1\)

\(\displaystyle 3a= - 1\)

\(\displaystyle 3a\div 3 = - 1 \div 3\)

\(\displaystyle a = - \frac{1}{3}\)

 

Example Question #1762 : Hspt Mathematics

Define an operation \(\displaystyle \bigstar\) on the set of real numbers as follows:

\(\displaystyle a \bigstar b = \frac{a+b}{ab}\).

If \(\displaystyle a \bigstar 0.5 = 0.1\),  then evaluate \(\displaystyle a\).

Possible Answers:

\(\displaystyle a = - \frac{ 19} {10}\)

\(\displaystyle a = \frac{10}{19}\)

\(\displaystyle a = \frac{ 19} {10}\)

\(\displaystyle a = - \frac{10}{19}\)

Correct answer:

\(\displaystyle a = - \frac{10}{19}\)

Explanation:

\(\displaystyle a \bigstar b = \frac{a+b}{ab}\),

so

\(\displaystyle a \bigstar 0.5 = \frac{a+0.5 }{a \cdot 0.5 } = \frac{a+0.5 }{0.5a }\)

Set this equal to 0.1:

\(\displaystyle \frac{a+0.5 }{0.5a } = 0.1\)

\(\displaystyle \frac{a+0.5 }{0.5a } \cdot 0.5 a = 0.1 \cdot 0.5 a\)

\(\displaystyle a+0.5 = 0.05 a\)

\(\displaystyle (a+0.5) \cdot 100 = 0.05 a \cdot 100\)

\(\displaystyle a \cdot 100 +0.5 \cdot 100 = 5 a\)

\(\displaystyle 100a +5 0= 5 a\)

\(\displaystyle 100a +50 - 100a = 5 a - 100a\)

\(\displaystyle 50 = -95a\)

\(\displaystyle 50 \div (-95) = -95a \div (-95)\)

\(\displaystyle a = -\frac{50}{95} = - \frac{10}{19}\)

Example Question #554 : Algebra

\(\displaystyle K\) is a number less than 36.

Which of the following gives a solution of the equation

\(\displaystyle |x- 17 | + K = 36\)

in terms of \(\displaystyle K\) ?

Possible Answers:

\(\displaystyle x = 53 - K\)

\(\displaystyle x = -53 - K\)

\(\displaystyle x = -19 - K\)

\(\displaystyle x = 19 - K\)

Correct answer:

\(\displaystyle x = 53 - K\)

Explanation:

\(\displaystyle |x- 17 | + K = 36\),

\(\displaystyle |x- 17 | + K - K = 36 - K\)

\(\displaystyle |x- 17 | = 36 - K\)

Since \(\displaystyle K < 36\), \(\displaystyle 36 - K > 0\), so solutions exist. One of the following two situations occurs:

\(\displaystyle x- 17 = 36 - K\)

\(\displaystyle x- 17 + 17 = 36 - K + 17\)

\(\displaystyle x = 53 - K\)

or

\(\displaystyle -(x- 17 )= 36 - K\)

\(\displaystyle -x+ 17 = 36 - K\)

\(\displaystyle -x+ 17 - 17 = 36 - K - 17\)

\(\displaystyle -x = 19 - K\)

\(\displaystyle -(-x )= -(19 - K)\)

\(\displaystyle x = K - 19\)

 

Of these two, only \(\displaystyle x = 53 - K\) is among the choices, so it is the correct choice.

Example Question #1763 : Hspt Mathematics

If \(\displaystyle L < 32\), then which of the following is equivalent to the expression \(\displaystyle | L - 32 | + 12\) ?

Possible Answers:

\(\displaystyle 44 + L\)

\(\displaystyle 44 - L\)

\(\displaystyle 20-L\)

\(\displaystyle 20+L\)

Correct answer:

\(\displaystyle 44 - L\)

Explanation:

If \(\displaystyle L < 32\), then \(\displaystyle L - 32 < 0\), so

\(\displaystyle | L - 32 | + 12\)

\(\displaystyle = -(L - 32 )+ 12\)

\(\displaystyle = - L + 32 + 12\)

\(\displaystyle = - L + 44\)

\(\displaystyle = 44 - L\)

Example Question #1171 : Concepts

If \(\displaystyle L > 47\), then which of the following is equivalent to the expression \(\displaystyle | L - 47 | - 32\) ?

Possible Answers:

\(\displaystyle - L + 79\)

\(\displaystyle L - 15\)

\(\displaystyle - L + 15\)

\(\displaystyle L - 79\)

Correct answer:

\(\displaystyle L - 79\)

Explanation:

If \(\displaystyle L > 47\), then \(\displaystyle L - 47 > 0\), so

\(\displaystyle | L - 47 | - 32\)

\(\displaystyle = L - 47 - 32\)

\(\displaystyle = L - 79\)

Example Question #1172 : Concepts

If \(\displaystyle 4< X< 12\), then 

\(\displaystyle |X - 12| + |X- 4|\)

can be rewritten as which of the following?

Possible Answers:

\(\displaystyle 16\)

\(\displaystyle 2X-16\)

\(\displaystyle -2X + 16\)

\(\displaystyle 8\)

Correct answer:

\(\displaystyle 8\)

Explanation:

If \(\displaystyle X > 4\), then

\(\displaystyle X - 4 >0\), so

\(\displaystyle |X- 4| = X-4\).

If \(\displaystyle X< 12\), then

\(\displaystyle X - 12 < 0\), so

\(\displaystyle |X- 12| = -(X-12)= -X + 12\)

\(\displaystyle |X - 12| + |X- 4|\)

\(\displaystyle = X-4 + (-X + 12)\)

\(\displaystyle = X-X -4 + 12\)

\(\displaystyle = 8\)

 

Example Question #1173 : Concepts

If \(\displaystyle X< 4\), then

\(\displaystyle |X - 12| + |X- 4|\)

can be rewritten as which of the following?

Possible Answers:

\(\displaystyle 16\)

\(\displaystyle -2X + 16\)

\(\displaystyle 2X-16\)

\(\displaystyle 8\)

Correct answer:

\(\displaystyle -2X + 16\)

Explanation:

If \(\displaystyle X < 4\), then

\(\displaystyle X - 4 < 0\), so

\(\displaystyle |X- 4| = -(X-4)= -X + 4\).

Also,

\(\displaystyle X - 12 < 4 - 12 = -8 < 0\), so

\(\displaystyle |X- 12| = -(X-12)= -X + 12\)

Therefore,

\(\displaystyle |X - 12| + |X- 4|\)

\(\displaystyle = (-X + 4)+ (-X + 12)\)

\(\displaystyle = -2X + 16\)

Example Question #1764 : Hspt Mathematics

Define an operation \(\displaystyle \bigstar\) on the set of real numbers as follows:

\(\displaystyle a \bigstar b = \frac{a+b}{ab}\).

\(\displaystyle a \bigstar (-1) = 1\). What is the value of \(\displaystyle a\) ?

Possible Answers:

\(\displaystyle a = \frac{1}{2}\)

\(\displaystyle a= 2\)

\(\displaystyle a = - \frac{1}{2}\)

\(\displaystyle a= -2\)

Correct answer:

\(\displaystyle a = \frac{1}{2}\)

Explanation:

\(\displaystyle a \bigstar b = \frac{a+b}{ab}\)

and

\(\displaystyle a \bigstar (-1) = 1\)

so

\(\displaystyle \frac{a+(-1)}{a(-1)}=1\)

\(\displaystyle \frac{a-1}{-a} = 1\)

\(\displaystyle \frac{a-1}{-a} \cdot (-a) = 1 \cdot (-a)\)

\(\displaystyle a- 1 = -a\)

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

\(\displaystyle 2a= 1\)

\(\displaystyle 2a \div 2 = 1 \div 2\)

\(\displaystyle a = \frac{1}{2}\)

Example Question #1172 : Concepts

Solve for \(\displaystyle x\)

\(\displaystyle 4x+6=30\)

Possible Answers:

\(\displaystyle x=20\)

\(\displaystyle x=9\)

\(\displaystyle x=6\)

\(\displaystyle x=30\)

Correct answer:

\(\displaystyle x=6\)

Explanation:

The first step to solve for \(\displaystyle x\) is to undue the \(\displaystyle 6\) by subtracting it from both sides of the equation.  

This results in having 

\(\displaystyle 4x=24\).  

Then you must undue \(\displaystyle 4*x\) by dividing by \(\displaystyle 4\) on each side resulting in an answer of 

\(\displaystyle 24/4=6\).

Example Question #1765 : Hspt Mathematics

Define an operation \(\displaystyle \bigstar\) on the set of real numbers as follows:

\(\displaystyle a \bigstar b = \frac{ab}{a+b}\)

\(\displaystyle a \bigstar 1= -1\). What is the value of \(\displaystyle a\) ?

Possible Answers:

\(\displaystyle a = -2\)

\(\displaystyle a = -0.5\)

\(\displaystyle a = -1\)

No real value of \(\displaystyle a\) makes this true.

Correct answer:

\(\displaystyle a = -0.5\)

Explanation:

\(\displaystyle a \bigstar b = \frac{ab}{a+b}\), so

\(\displaystyle a \bigstar 1 = \frac{a \cdot 1 }{a+1} = \frac{a }{a+1}\)

Set this equal to \(\displaystyle -1\):

\(\displaystyle \frac{a }{a+1} = -1\)

\(\displaystyle \frac{a }{a+1} \cdot (a+1) = -1 \cdot (a+1)\)

\(\displaystyle a = -a - 1\)

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

\(\displaystyle 2a = - 1\)

\(\displaystyle 2a \div 2= - 1 \div 2\)

\(\displaystyle a = -0.5\)

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