ISEE Middle Level Quantitative : ISEE Middle Level (grades 7-8) Quantitative Reasoning

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

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Example Questions

Example Question #3 : How To Find The Area Of A Triangle

Right triangle 3

The above figure gives the lengths of the three sides of the triangle in feet. Give its area in square inches.

Possible Answers:

\(\displaystyle 12A+ 12 B + 12 C\)

\(\displaystyle 6A+6B +6C\)

\(\displaystyle 72AB\)

\(\displaystyle 6AB\)

Correct answer:

\(\displaystyle 72AB\)

Explanation:

The area of a right triangle is half the product of the lengths of its legs, which here are \(\displaystyle A\) feet and \(\displaystyle B\) feet.

Multiply each length by 12 to convert to inches - the lengths become \(\displaystyle 12A\) and \(\displaystyle 12 B\). The area in square inches is therefore

\(\displaystyle \frac{1}{2} (12A )(12 B) = \frac{1}{2} \cdot 12 \cdot 12 \cdot A \cdot B = 72AB\) square inches.

Example Question #245 : Plane Geometry

Pentagon

Figure NOT drawn to scale

Square \(\displaystyle ABCD\) has area 1,600. \(\displaystyle AX = BY\)\(\displaystyle AZ = 16\). Which of the following is the greater quantity?

(a) The area of \(\displaystyle \bigtriangleup AZX\)

(b) The area of \(\displaystyle \bigtriangleup BZY\)

Possible Answers:

(a) and (b) are equal

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

(a) is the greater quantity

(b) is the greater quantity

Correct answer:

(b) is the greater quantity

Explanation:

Square \(\displaystyle ABCD\) has area 1,600, so the length of each side is \(\displaystyle \sqrt{1,600 }= 40\).

Since \(\displaystyle AZ = 16\),

\(\displaystyle BZ = AB - AZ = 40 - 16 = 24\)

Therefore, \(\displaystyle BZ > AZ\).

\(\displaystyle \bigtriangleup AZX\) has as its area \(\displaystyle \frac{1}{2} \cdot AX \cdot AZ\)\(\displaystyle \bigtriangleup BZY\) has as its area \(\displaystyle \frac{1}{2} \cdot BX \cdot BZ\).

Since \(\displaystyle BZ > AZ\) and \(\displaystyle AX = BX\), it follows that

\(\displaystyle BX \cdot BZ > AX \cdot AZ\)

and

\(\displaystyle \frac{1}{2} \cdot BX \cdot BZ >\frac{1}{2} \cdot AX \cdot AZ\)

\(\displaystyle \bigtriangleup BZY\) has greater area than \(\displaystyle \bigtriangleup AZX\).

Example Question #3 : How To Find The Area Of A Triangle

Square 1

Figure NOT drawn to scale.

In the above diagram, Square \(\displaystyle SUAE\) has area 400. Which is the greater quantity?

(a) The area of \(\displaystyle \bigtriangleup SQE\)

(b) The area of \(\displaystyle \bigtriangleup UAR\)

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:

Square \(\displaystyle SUAE\) has area 400, so its common sidelength is the square root of 400, or 20. Therefore, 

\(\displaystyle AR = AE- ER = 20 - 9 = 11\).

The area of a right triangle is half the product of the lengths of its legs.

\(\displaystyle \bigtriangleup SQE\) has legs \(\displaystyle \overline{SQ}\) and \(\displaystyle \overline{SE}\), so its area is

\(\displaystyle \frac{1}{2} \cdot SQ \cdot SE = \frac{1}{2} \cdot 9 \cdot 20 = 90\).

\(\displaystyle \bigtriangleup UAR\) has legs \(\displaystyle \overline{UA}\) and \(\displaystyle \overline{AR}\), so its area is

\(\displaystyle \frac{1}{2} \cdot AR \cdot UA = \frac{1}{2} \cdot 11 \cdot 20 = 110\).

\(\displaystyle \bigtriangleup UAR\) has the greater area.

Example Question #4 : How To Find The Area Of A Triangle

Parallelogram 1

Figure NOT drawn to scale

The above diagram depicts Parallelogram \(\displaystyle ABCD\). Which is the greater quantity?

(a) The area of \(\displaystyle \bigtriangleup AMD\)

(b) The area of \(\displaystyle \bigtriangleup BMC\)

Possible Answers:

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

(a) is the greater quantity

(a) and (b) are equal

Correct answer:

(a) and (b) are equal

Explanation:

Opposite sides of a parallelogram have the same measure, so

\(\displaystyle AB = CD\)

\(\displaystyle AM + MB = CD\)

\(\displaystyle 60 + MB = 120\)

\(\displaystyle 60 + MB - 60 = 120 - 60\)

\(\displaystyle MB = 60\)

 Base \(\displaystyle \overline{AM}\) of \(\displaystyle \bigtriangleup AMD\) and base \(\displaystyle \overline{MB}\) of \(\displaystyle \bigtriangleup BMC\) have the same length;  also, as can be seen below, both have the same height, which is the height of the parallelogram.

Parallelogram 1

Therefore, the areas of \(\displaystyle \bigtriangleup AMD\) and \(\displaystyle \bigtriangleup BMC\) have the same area - \(\displaystyle \frac{1}{2} \cdot 60 \cdot h = 30h\).

Example Question #2 : How To Find The Area Of A Triangle

Right triangle 2

Refer to the above figure. Which is the greater quantity?

(a) The perimeter of the triangle

(b) 3 feet

Possible Answers:

(a) is the greater quantity

(b) is the greater quantity

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

(a) and (b) are equal

Correct answer:

(b) is the greater quantity

Explanation:

The perimeter of the triangle - the sum of the lengths of its sides - is

\(\displaystyle 5 + 12 + 13 = 30\) inches. 

3 feet are equivalent to \(\displaystyle 3 \times 12 = 36\) inches, so this is the greater quantity.

Example Question #252 : Plane Geometry

Which is the greater quantity?

(a) 370 meters

(b) 3,700 centimeters

Possible Answers:

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

(a) and (b) are equal

(a) is the greater quantity

(b) is the greater quantity

Correct answer:

(a) is the greater quantity

Explanation:

One meter is equivalent to 100 centimeters, so 370 meters can be converted to centimeters by multiplying by 100:

\(\displaystyle 370 \times 100 = 37,000\).

370 meters are equal to 37.000 centimeters and is the greater quantity.

Example Question #1 : How To Find Length Of A Line

Which is the greater quantity?

(a) 4.8 kilometers

(b) 4,800 meters

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 kilometer is equal to 1,000 meters, so convert 4.8 kilometers to meters by multiplying by 1,000:

\(\displaystyle 4.8 \times 1,000 = 4,800\) meters

The two quantities are equal.

Example Question #1 : How To Find Length Of A Line

A regular pentagon has perimeter 1 yard. Give the length of one side.

Possible Answers:

\(\displaystyle 7 \frac{1}{5 } \textrm{ in}\)

\(\displaystyle 6 \textrm{ in}\)

\(\displaystyle 4 \frac{1}{2} \textrm{ in}\)

\(\displaystyle 9\textrm{ in}\)

Correct answer:

\(\displaystyle 7 \frac{1}{5 } \textrm{ in}\)

Explanation:

A regular pentagon has five sides of equal length. The perimeter, which is the sum of the lengths of these sides, is one yard, which is equal to 36 inches. Therefore, the length of one side is

\(\displaystyle 36 \textrm{ in} \div 5 = 7\frac{1}{5} \textrm{ in}\).

Example Question #253 : Plane Geometry

A regular hexagon has perimeter 8 feet. Give the length of one side.

Possible Answers:

12 inches

24 inches

16 inches

18 inches

Correct answer:

16 inches

Explanation:

The perimeter can be converted from feet to inches by multiplying by conversion factor 12 {inches per foot): 

\(\displaystyle 8 \textrm{ ft} \times 12 \textrm{ in/ft} = 96 \textrm{ in}\)

A regular hexagon has six sides of equal length. Divide this perimeter by 6 to obtain the length of each side:

\(\displaystyle 96 \textrm{ in} \div 6 = 16 \textrm{ in}\)

Example Question #1 : How To Find The Volume Of A Net

Which is the greater quantity?

(a) The sidelength of a cube with surface area \(\displaystyle 600 \textrm{ cm}^{2}\)

(b) The sidelength of a cube with volume \(\displaystyle 1,000 \textrm{ cm}^{3}\)

Possible Answers:

(a) is greater

It is impossible to tell from the information given

(b) is greater

(a) and (b) are equal

Correct answer:

(a) and (b) are equal

Explanation:

(a) A cube has six faces, each a square. Since the surface area of this cube is \(\displaystyle 600 \textrm{ cm}^{2}\), each face has one-sixth this area, or \(\displaystyle 100 \textrm{ cm}^{2}\); the sidelength is the square root of this, or \(\displaystyle 10 \textrm{ cm}\).

(b) The volume of a cube is the cube of its sidelength, so we take the cube root of the volume of this cube to get the sidelength: 

\(\displaystyle \sqrt[3]{1,000} = 10 \textrm{ cm}\)

The cubes have the same sidelength.

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