ISEE Upper Level Quantitative : How to find the length of the side of a triangle

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

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Example Questions

Example Question #11 :Triangles

Which of the following could be the lengths of the three sides of a scalene triangle?

Possible Answers:

All of the other choices are possible lengths of a scalene triangle

Correct answer:

All of the other choices are possible lengths of a scalene triangle

Explanation:

A scalene triangle, by definition, has sides all of different lengths. Since all of the given choices fit that criterion, the correct choice is that all can be scalene.

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

鉴于with right angle,.

Which is the greater quantity?

(a)

(b)

Possible Answers:

It is impossible to tell from the information given

(a) and (b) are equal

(b) is greater

(a) is greater

Correct answer:

(a) is greater

Explanation:

The sum of the measures of the angles of a triangle is 180, so

, so the side opposite, which is, is longer than the side opposite, which is. This makes (a) the greater quantity.

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

鉴于with obtuse angle, which is the greater quantity?

(a)

(b)

Possible Answers:

(b) is greater.

(a) is greater.

(a) and (b) are equal.

It is impossible to tell from the information given.

Correct answer:

(b) is greater.

Explanation:

To compare the lengths of一个dfrom the angle measures, it is necessary to know which of their opposite angles -一个d, respectively - is the greater angle. Sinceis the obtuse angle, it has the greater measure, andis the longer side. This makes (b) greater.

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

has obtuse angle;. Which is the greater quantity?

(a)

(b)

Possible Answers:

(b) is greater.

(a) and (b) are equal.

It is impossible to tell from the information given.

(a) is greater.

Correct answer:

(a) is greater.

Explanation:

Sinceis the obtuse angle of,

.

,

,

so (a) is the greater quantity.

Example Question #5 :How To Find The Length Of The Side Of A Triangle

鉴于with. Which is the greater quantity?

(a)

(b)

Possible Answers:

(a) is greater.

(a) and (b) are equal.

(b) is greater.

It is impossible to tell from the information given.

Correct answer:

(b) is greater.

Explanation:

Use the Triangle Inequality:

This makes (b) the greater quantity.

Example Question #6 :How To Find The Length Of The Side Of A Triangle

鉴于with. Which is the greater quantity?

(a)

(b)

Possible Answers:

(b) is greater.

(a) is greater.

(a) and (b) are equal.

It is impossible to tell from the information given.

Correct answer:

It is impossible to tell from the information given.

Explanation:

By the Converse of the Pythagorean Theorem,

if and only ifis a right angle.

However, ifis acute, then; ifis obtuse, then.

Since we do not know whetheris acute, right, or obtuse, we cannot determine whether (a) or (b) is greater.

Example Question #7 :How To Find The Length Of The Side Of A Triangle

is acute;. Which is the greater quantity?

(a)

(b)

Possible Answers:

It is impossible to tell from the information given.

(a) and (b) are equal.

(a) is greater.

(b) is greater.

Correct answer:

(b) is greater.

Explanation:

Sinceis an acute triangle,is an acute angle, and

,

(b) is the greater quantity.

Example Question #21 :Geometry

鉴于:.. Which is the greater quantity?

(a) 18

(b)

Possible Answers:

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

(a) is the greater quantity

(b) is the greater quantity

(a) and (b) are equal

Correct answer:

(a) is the greater quantity

Explanation:

Suppose there exists a second trianglesuch that一个d. Whether, the angle opposite the longest side, is acute, right, or obtuse can be determined by comparing the sum of the squares of the lengths of the shortest sides to the square of the length of the longest:

, makingobtuse, so.

We know that

一个d

.

Between一个d, we have two sets of congruent sides, with the included angle of the latter of greater measure than that of the former. It follows from the Side-Angle-Side Inequality (or Hinge) Theorem that between the third sides,is the longer. Therefore,

.

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