ISEE Upper Level Quantitative : ISEE Upper Level (grades 9-12) Quantitative Reasoning

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

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Example Questions

Example Question #221 : Isee Upper Level (Grades 9 12) Quantitative Reasoning

The sidelength of Square A is three-sevenths that of Square B. What is the ratio of the area of Square B to that of Square A?

Possible Answers:

\(\displaystyle 7\textrm{ to }3\)

\(\displaystyle 49 \textrm{ to } 9\)

\(\displaystyle 14\textrm{ to }3\)

\(\displaystyle 9\textrm{ to }7\)

None of the other answers give the correct ratio.

Correct answer:

\(\displaystyle 49 \textrm{ to } 9\)

Explanation:

Since the ratio is the same regardless of the sidelengths, then for simplicity's sake, assume the sidelength of Square B is 7. The area of Square B is therefore the square of this, or 49.

Then the sidelength of Square A is three-sevenths of 7, or 3. Its area is the square of 3, or 9. 

The ratio of the area of Square B to that of Square A is therefore 49 to 9.

Example Question #1 : How To Find The Area Of A Square

Five squares have sidelengths one foot, two feet, three feet, four feet, and five feet.

Which is the greater quantity?

(A) The mean of their areas

(B) The median of their areas

Possible Answers:

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

(A) is greater

(B) is greater

(A) and (B) are equal

Correct answer:

(A) is greater

Explanation:

The areas of the squares are:

\(\displaystyle 1^{2} = 1\) square foot

\(\displaystyle 2^{2} = 4\) square feet

\(\displaystyle 3^{2} = 9\) square feet

\(\displaystyle 4^{2}= 16\) square feet

\(\displaystyle 5^{2}= 25\) square feet

Therefore, we are comparing the mean and the median of the set \(\displaystyle \left \{ 1, 4, 9, 16, 25\right \}\).

The mean of this set is the sum divided by 5:

 \(\displaystyle (1 + 4 + 9 + 16 + 25) \div 5 = 55 \div 5 = 11\) 

The median is the middle element after arrangement in ascending order, which is 9.

This makes (A), the mean, greater.

Example Question #6 : How To Find The Area Of A Square

Four squares have sidelengths one meter, 120 centimeters, 140 centimeters, and 140 centimeters. Which is the greater quantity?

(A) The mean of their areas

(B) The median of their areas

Possible Answers:

(A) and (B) are equal

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

(A) is greater

(B) is greater

Correct answer:

(B) is greater

Explanation:

The areas of the squares are:

\(\displaystyle 100 \cdot 100 = 10,000\) square centimeters (one meter being 100 centimeters)

\(\displaystyle 120 \cdot 120 = 14,400\) square centimeters

\(\displaystyle 140 \cdot 140 = 19,600\) square centimeters

\(\displaystyle 140 \cdot 140 = 19,600\) square centimeters

The mean of these four areas is their sum divided by four:

\(\displaystyle (10,000+14,400+19,600+19,600) \div 4\)

\(\displaystyle = 63,600 \div 4 =15,900\) square centimeters.

The median is the mean of the two middle values, or

\(\displaystyle ( 14,400+19,600 ) \div 2 = 34,000 \div 2 = 17,000\) square centimeters.

The median, (B), is greater.

Example Question #9 : How To Find The Area Of A Square

The perimeter of a square is \(\displaystyle 12x+16\). Give the area of the square in terms of \(\displaystyle x\).

Possible Answers:

\(\displaystyle 144x^{2} + 256\)

\(\displaystyle 9x^{2}+24x + 16\)

\(\displaystyle 144x^{2} +384x+ 256\)

None of the other responses gives a correct answer.

\(\displaystyle 9x^{2} + 16\)

Correct answer:

\(\displaystyle 9x^{2}+24x + 16\)

Explanation:

The length of one side of a square is one fourth its perimeter. Since the perimeter of the square is \(\displaystyle 12x+16\), the length of one side is

\(\displaystyle (12x+16) \div 4 = 3x+ 4\)

The area of the square is the square of this sidelength, or

\(\displaystyle ( 3x+ 4)^{2}= (3x)^{2}+ 2 \cdot 3x \cdot 4 + 4 ^{2} = 9x^{2}+24x + 16\)

Example Question #5 : How To Find The Area Of A Square

The sidelength of a square is \(\displaystyle 2^{x}\). Give its area in terms of \(\displaystyle x\).

Possible Answers:

\(\displaystyle 2 ^{4 x}\)

\(\displaystyle 2 ^{x+1}\)

\(\displaystyle 2 ^{x+2}\)

\(\displaystyle 2 ^{2 x}\)

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

Correct answer:

\(\displaystyle 2 ^{2 x}\)

Explanation:

The area of a square is the square of its sidelength. Therefore, square \(\displaystyle 2^{x}\):

\(\displaystyle \left (2^{x} \right ) ^{2} = 2 ^{2 x}\)

Example Question #222 : Isee Upper Level (Grades 9 12) Quantitative Reasoning

A diagonal of a square has length \(\displaystyle 2^{x}\). Give its area.

Possible Answers:

\(\displaystyle 2^{2x- \frac{1}{2}}\)

\(\displaystyle 2^{2x}\)

\(\displaystyle 2^{2x+ \frac{1}{2}}\)

\(\displaystyle 2^{2x-1}\)

\(\displaystyle 2^{2x+1}\)

Correct answer:

\(\displaystyle 2^{2x-1}\)

Explanation:

A square being a rhombus, its area can be determined by taking half the product of the lengths of its (congruent) diagonals:

\(\displaystyle A = \frac{1}{2} \cdot 2^{x} \cdot 2^{x} = 2 ^{-1} \cdot 2^{x} \cdot 2^{x} = 2^{-1 + x + x } = 2^{2x-1}\)

Example Question #223 : Geometry

The lengths of the sides of ten squares form an arithmetic sequence. One side of the smallest square measures sixty centimeters; one side of the second-smallest square measures one meter. 

Give the area of the largest square, rounded to the nearest square meter.

Possible Answers:

20 square meters

18 square meters

24 square meters

16 square meters

22 square meters

Correct answer:

18 square meters

Explanation:

Let \(\displaystyle a_{n}\) be the lengths of the sides of the squares in meters. \(\displaystyle a_{1} = 60 \div 100 = 0.6\) and \(\displaystyle a_{2} = 1\), so their common difference is

\(\displaystyle d =1 - 0.6 = 0.4\)

The arithmetic sequence formula is 

\(\displaystyle a_{n} = a_{1} + (n-1)d\)

The length of a side of the largest square - square 10 - can be found by substituting \(\displaystyle a_{1} = 0.6, n= 10, d = 0.4\):

\(\displaystyle a_{10} =0.6+ (10-1) 0.4 = 0.6 + 9 (0.4) = 0.6 + 3.6 = 4.2\) 

The largest square has sides of length 4.2 meters, so its area is the square of this, or \(\displaystyle A = 4.2^{2} = 17.64\) square meters.

Of the choices, 18 square meters is closest.

Example Question #21 : Squares

The areas of six squares form an arithmetic sequence. The smallest square has perimeter 16; the second smallest square has perimeter 20. Give the area of the largest of the six squares.

Possible Answers:

\(\displaystyle 81\)

\(\displaystyle 61\)

\(\displaystyle 70\)

\(\displaystyle 100\)

\(\displaystyle 36\)

Correct answer:

\(\displaystyle 61\)

Explanation:

The two smallest squares have perimeters 16 and 20, so their sidelengths are one fourth of these, or, respectively, 4 and 5. Their areas are the squares of these, or, respectively, 16 and 25. Therefore, in the arithmetic sequence,

\(\displaystyle A_{1} = 16\)

\(\displaystyle A_{2} = 25\)

and the common difference is \(\displaystyle d = 25 - 16 = 9\).

The area of the \(\displaystyle n\)th smallest square is

\(\displaystyle A_{n}= A_{1}+ (n-1)d\)

Setting \(\displaystyle A_{1} = 16, n = 6, d=9\), the area of the largest (or sixth-smallest) square is

\(\displaystyle A_{n}= 16+ (6-1)9 = 16 + 5 \cdot 9 = 16 + 45 = 61\)

Example Question #223 : Isee Upper Level (Grades 9 12) Quantitative Reasoning

Which is the greater quantity?

(a) The area of a square with sides of length \(\displaystyle 4X\) meters

(b) The area of a square with perimeter \(\displaystyle 160 X\) centimeters

Possible Answers:

It cannot be determined which of (a) and (b) is greater

(b) is the greater quantity

(a) is the greater quantity

(a) and (b) are equal

Correct answer:

(a) is the greater quantity

Explanation:

A square with perimeter \(\displaystyle 160 X\) centimeters has sides of length one-fourth of this, or \(\displaystyle 160 X \div 4 = 40 X\) centimeters. Since one meter is equal to 100 centimeters, divide by 100 to get the equivalent in meters - this is 

\(\displaystyle 40 X \div 100 = 0.4X\)

meters.

The square in (b) has sidelength less than that of the square in (a), so its area is also less than that in (a).

Example Question #23 : Squares

On the coordinate plane, Square A has as one side a segment with its endpoints at the origin and at the point with coordinates \(\displaystyle (A, B)\). Square B has as one side a segment with its endpoints at the origin and at the point with coordinates \(\displaystyle (-B, -A)\)\(\displaystyle A\) and \(\displaystyle B\) are both positive numbers and \(\displaystyle B > A\). Which is the greater quantity?

(a) The area of Square A

(b) The area of Square B

Possible Answers:

(a) and (b) are equal

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

(b) is the greater quantity

(a) is the greater quantity

Correct answer:

(a) and (b) are equal

Explanation:

The length of a segment with endpoints \(\displaystyle (0,0)\) and \(\displaystyle (A, B)\) can be found using the distance formula with \(\displaystyle x_{1} = y_{1} = 0\)\(\displaystyle x_{2} = A\)\(\displaystyle y_{2} = B\):

\(\displaystyle d = \sqrt{(x_{2}- x_{1})^{2}+(y_{2}-y_{1})^{2}}\)

\(\displaystyle d = \sqrt{(A-0)^{2}+(B-0)^{2}}\)

\(\displaystyle d = \sqrt{A ^{2}+B^{2}}\)

The length of a segment with endpoints \(\displaystyle (0,0)\) and \(\displaystyle (-B, -A)\) can be found using the distance formula with \(\displaystyle x_{1} = y_{1} = 0\)\(\displaystyle x_{2} = -B\)\(\displaystyle y_{2} = -A\):

\(\displaystyle d = \sqrt{(x_{2}- x_{1})^{2}+(y_{2}-y_{1})^{2}}\)

\(\displaystyle d = \sqrt{(-B-0)^{2}+(-A-0)^{2}}\)

\(\displaystyle d = \sqrt{(-B )^{2}+(-A )^{2}}\)

\(\displaystyle d = \sqrt{B^{2}+A ^{2}}\)

\(\displaystyle d = \sqrt{A ^{2}+B^{2}}\)

 

The sides are of equal length, so the squares have equal area. Note that the fact that \(\displaystyle B > A\) is irrelevant to the question.

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