ISEE Upper Level Quantitative : Algebraic Concepts

Study concepts, example questions & explanations for ISEE Upper Level Quantitative

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Example Questions

Example Question #15 : Operations

Factor:

\(\displaystyle y^{4} - x^{2} + 8x - 16\)

Possible Answers:

\(\displaystyle (y ^{2}+ x -4) ^{2}\)

\(\displaystyle (y ^{2}- x -4) (y ^{2}- x +4)\)

\(\displaystyle (y ^{2}- x +4) ^{2}\)

\(\displaystyle (y ^{2}+ x +4) (y ^{2}- x -4)\)

\(\displaystyle (y ^{2}+ x -4) (y ^{2}- x +4)\)

Correct answer:

\(\displaystyle (y ^{2}+ x -4) (y ^{2}- x +4)\)

Explanation:

We can rewrite as follows:

\(\displaystyle y^{4} - x^{2} + 8x - 16\)

\(\displaystyle = y^{4} - (x^{2} - 8x + 16)\)

 

\(\displaystyle y^{4} = \left (y ^{2} \right )^{2}\), and 

\(\displaystyle x^{2} - 8x + 16\) is a perfect square polynomial, as seen here:

\(\displaystyle x^{2} - 8x + 16 = x^{2} - 2 \cdot 4 \cdot x + 4^{2} = (x -4)^{2}\)

so the original polynomial is equal to 

\(\displaystyle \left (y ^{2} \right )^{2} - (x -4)^{2}\)

This is the difference of squares, so it can be factored as

\(\displaystyle \left [y ^{2} + (x -4) \right ]\left [y ^{2} - (x -4) \right ]\)

\(\displaystyle = (y ^{2}+ x -4) (y ^{2}- x +4)\)

Example Question #16 : Operations

If m is a negative integer, which of the following is an expression that also represents a positive integer?

Possible Answers:

\(\displaystyle 5m^{3}-2m\)

\(\displaystyle 5m^{3}+2m^{3}\)

\(\displaystyle 5m+2m\)

\(\displaystyle 5m^{2}-2m\)

Correct answer:

\(\displaystyle 5m^{2}-2m\)

Explanation:

The easiest way to solve this problem is to take a negative integer to use for m. 

For example, \(\displaystyle -2\) can be used. 

Plugging in \(\displaystyle -2\) into the expression, \(\displaystyle 5m^{2}-2m\), we get:

\(\displaystyle 5\cdot (-2^{2})-2\cdot (-2)\)

This simplifies to 

\(\displaystyle 5\cdot 4+4\)

\(\displaystyle 20+4\)

\(\displaystyle 24\)

Given that 24 is a positive number, \(\displaystyle 5m^{2}-2m\) is the correct answer. 

Example Question #181 : Algebraic Concepts

When evaluating the expression

\(\displaystyle \left [a-(b\div c)^{3} \right ] + d \cdot e\),

assuming you know the values of all five variables, what is the last operation that must be performed?

Possible Answers:

Cubing

Multiplication

Addition

Division

Subtraction

Correct answer:

Addition

Explanation:

By the order of operations, all operations within grouping symbols must be performed first, with the innermost symbols taking precedence. Therefore, the three operations within the brackets - the subtraction, the division, and the cubing - must be performed before the remaining two.

Once these three operations are completed, there remain two more, a division and an addition. Division has precendence in the order of operations, so the last operation performed is the addition.

Example Question #182 : Algebraic Concepts

Which is the greater quantity?

(a) The number of miles in 100 kilometers

(b) The number of kilometers in 100 miles 

Note: You may use the conversion factor 1 mile = 1.609 kilometers.

Possible Answers:

It is impossible to determine which is greater from the information given

(b) is the greater quantity

(a) is the greater quantity

(a) and (b) are equal

Correct answer:

(b) is the greater quantity

Explanation:

Since 1 mile is equivalent to 1.609 kilometers, the number of kilometers equivalent to 100 miles can be found by multiplying 100 by 1.609. Conversely, the number of miles equivalent to 100 kilometers can be found by dividing 100 by 1.609. 

You do not have to do the actual math to answer the question. Since the conversion factor is greater than one, multiplying any positive number by this factor yields a result greater than dividing that same number by it. Therefore, 

\(\displaystyle 100 \times 1.609 > 100 \div 1.609\),

and the number of kilometers equivalent to 100 miles, (b), is the greater quantity.

Example Question #183 : Algebraic Concepts

\(\displaystyle x\) is a positive number. Which is the greater quantity?

(a) The number of inches in \(\displaystyle 16 x\) feet

(b) The number of ounces in \(\displaystyle 12x\) pounds

Possible Answers:

(b) is the greater quantity

(a) is the greater quantity

It is impossible to determine which is greater from the information given

(a) and (b) are equal

Correct answer:

(a) and (b) are equal

Explanation:

One foot comprises twelve inches, so multiply the number of feet by conversion factor 12:

\(\displaystyle 16x \cdot 12 = 192x\) inches.

One pound comprises sixteen ounces, so multiply the number of ounces by conversion factor 16:

\(\displaystyle 12x \cdot 16 = 192x\) ounces.

The two quantities are both equal to \(\displaystyle 192x\).

Example Question #184 : Algebraic Concepts

Which is the greater quantity?

(a) The number of inches in \(\displaystyle \frac{7}{36} x\) yards

(b) The number of days in \(\displaystyle \frac{36}{7}x\) weeks

Possible Answers:

(a) is the greater quantity

(a) and (b) are equal

It is impossible to determine which is greater from the information given

(b) is the greater quantity

Correct answer:

(b) is the greater quantity

Explanation:

One yard comprises thirty-six inches, so multiply the number of yards by conversion factor 36:

\(\displaystyle \frac{7}{36}x \cdot 36 = 7x\)

One week comprises seven days, so multiply the number of weeks by conversion factor 7:

\(\displaystyle \frac{36} {7} x \cdot 7 = 36x\)

(b) is the greater quantity, since, if \(\displaystyle x\) is positive, \(\displaystyle 36x > 7x\).

Example Question #185 : Algebraic Concepts

\(\displaystyle t ^{2} = 40\)

\(\displaystyle u ^{2}= 17\)

Evaluate \(\displaystyle (2t+u) (2t-u)\).

Possible Answers:

\(\displaystyle 63\)

\(\displaystyle 177\)

\(\displaystyle 143\)

\(\displaystyle 97\)

Correct answer:

\(\displaystyle 143\)

Explanation:

\(\displaystyle (2t+u) (2t-u)\) is the product of the sum and the difference of the same two binomials, so this can be rewritten, and evaluated, using the difference of squares pattern:

\(\displaystyle (2t+u) (2t-u)\)

\(\displaystyle = (2 t)^{2} - u^{2}\)

\(\displaystyle = 2^{2} \cdot t ^{2} - u^{2}\)

\(\displaystyle = 4 t ^{2} - u^{2}\)

\(\displaystyle = 4 (40 ) - 17\)

\(\displaystyle = 160 - 17\)

\(\displaystyle = 143\)

 

Example Question #21 : Variables

The ratio of 10 to 14 is closest to what value?

Possible Answers:

0.24

0.04

0.71

0.57

Correct answer:

0.71

Explanation:

Another way to express ratios is through division. 10 divided by 14 is approximate 0.71.

Example Question #187 : Algebraic Concepts

If \(\displaystyle q\) is the quotient of \(\displaystyle p\) and \(\displaystyle v\), which statement could be true?

Possible Answers:

\(\displaystyle p\div q=v\)

\(\displaystyle v-p=q\)

\(\displaystyle p\div \ v=q\)

\(\displaystyle v p=q\)

\(\displaystyle p+v=q\)

Correct answer:

\(\displaystyle p\div \ v=q\)

Explanation:

A quotient is the result of division. If \(\displaystyle q\) is the quotient of \(\displaystyle p\) and \(\displaystyle v\), that means that \(\displaystyle p\div v=q\) could be true.

Example Question #188 : Algebraic Concepts

\(\displaystyle A\) is a negative integer. Which is the greater quantity?

(A) \(\displaystyle A \div \left ( - \frac{1}{3}\right )\)

(B) \(\displaystyle A \div \left ( -0.3\right )\)

Possible Answers:

(A) is greater

(B) is greater

It is impossible to tell which is greater from the information given

(A) and (B) are equal

Correct answer:

(B) is greater

Explanation:

Since the quotient of negative numbers is positive, both results will be positive.

We can rewrite both of these as products of positive numbers, as follows:

\(\displaystyle A \div \left ( - \frac{1}{3}\right ) = \left | A \right | \div \frac{1}{3} = \left | A \right | \cdot 3\)

\(\displaystyle A \div \left ( -0.3\right ) =A \div \left ( - \frac{3}{10}\right ) = \left | A \right | \div \frac{3}{10} = \left | A \right | \cdot \frac{10}{3} = \left | A \right | \cdot 3 \frac{1}{3}\)

\(\displaystyle 3 \frac{1}{3} > 3\), so

\(\displaystyle \left | A \right | \cdot 3 \frac{1}{3} >\left | A \right | \cdot 3\), and 

\(\displaystyle A \div \left ( -0.3\right ) > A \div \left ( - \frac{1}{3}\right )\)

making (B) greater.

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