Math Explorer · Chapter 5
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Lesson 5.7 — Chapter 5 Exercise: Equal-Area Transformations

Lesson 5.7 · Chapter exercise

Equal-Area Transformations

Apply shared-base and shared-height reasoning, area ratios, side extensions, trapezoid and parallelogram networks, area ledgers, and multistep equal-area chains.

Grade 5 enrichment 15 questions 120 points Diagrams not necessarily to scale

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Tips for this exercise

Section A · Fill inQuestions 1–10 are worth 6 points each. Enter every requested value or comparison sign.
Section B · Extended responseQuestions 11–15 are worth 12 points each. Record a final answer and show enough working to explain your method, then compare it with exercise review.

Section A — Fill in

Enter the requested value, fraction, count, or comparison sign.

10 × 6 = 60 points
1

Compare the two regions

Not answered

Triangle ABC is divided by segment ED into Regions I and II. E lies between A and B, and D lies between B and C. Given

BD = DC = 4,   BE = 3,   AE = 6.

The area of Region II is ______ times the area of Region I.

ABC ED III 36 44

Region I is triangle BED; Region II is the remaining part.

times
Optional scratch work
2

A trapezoid area network

Not answered

BD is a diagonal of trapezoid ABCD, whose parallel bases are AD and BC. E lies between B and C. Segment AE is parallel to leg DC, and AE intersects BD at O.

Area(△BOE) is 4 cm² greater than Area(△AOD), and EC = 3/8 BC.

Find the area of trapezoid ABCD.

ABCD EO EC = 3/8 BC

AE ∥ DC. Diagram not necessarily to scale.

cm²
Optional scratch work
3

A diagonal in a parallelogram

Not answered

In parallelogram ABCD, BC = 3 cm. The perpendicular height from A to BC is AE = 2 cm.

Find the area of triangle ACD.

ABCDE BC = 3 cmAE = 2 cm

AE ⟂ BC.

cm²
Optional scratch work
4

Compare four triangle areas

Not answered

In parallelogram MNOP, Q is a point strictly between the endpoints of side OP. Lines MO and NQ intersect at R.

Fill each blank with >, <, or =.

Area(△MRQ) ____ Area(△NRO)
Area(△MRN) ____ Area(△QRO)
MPON QR

Q lies strictly between O and P.

Optional scratch work
5

Count equal-area triangles

Not answered

In parallelogram ABCD, E and F are the midpoints of AD and CD, respectively.

How many other triangles in the diagram have the same area as triangle BFC? Count triangles whose three sides follow drawn segments, including triangles made of several smaller pieces. Exclude the reference triangle itself.

ABCD EF

E and F are midpoints. Count triangles other than △BFC itself.

triangles
Optional list or scratch work
6

A midpoint and a point on a median

Not answered

In triangle ABC, D is the midpoint of BC, and point E lies on AD with

DE = 2/5 AD.

The area of triangle ABC is ______ times the area of triangle CDE.

ABCDE DE = 2/5 AD

D is the midpoint of BC.

times
Optional scratch work
7

Two ratios in one large triangle

Not answered

In the diagram, points D, A, and C lie on one straight line in that order, while E lies on CB. Given

AC = 4AD, and Area(△CDE) = 1/2 Area(△ABC).

Complete the relationship: BE = ______ × BC.

CBDAE AC = 4AD

The drawing shows the incidences, not the true scale.

of BC
Optional scratch work
8

Eight equal divisions and an area invariant

Not answered

Triangles ABC and BCD share base BC. Segments AD and BC intersect at E, with AE = ED and ADBC.

Divide BC into eight equal parts. Let F be the first division point from B, and the intersection E is the second division point from B. Connect every division point to both A and D.

How many other triangles in the diagram have the same area as triangle ABF? Count triangles whose three sides follow drawn segments, including triangles made of several smaller pieces. Exclude the reference triangle itself.

ADBCFE

F is the first eighth-point; E is the second.

triangles
Optional list or scratch work
9

Two shaded corner triangles

Not answered

In the trapezoid, the top base is parallel to BC and BC = 5. The perpendicular distance between the top base and BC is 5. The perpendicular distance from the intersection point A to BC is 2.

Find the sum of the areas of the two shaded triangles.

ABC 5 5 2

The two diagonals meet at A.

square units
Optional scratch work
10

Three small regular hexagons

Not answered

A large regular hexagon has area 24 cm². Three congruent small regular hexagons are placed inside it. Each small hexagon has two opposite vertices at the large hexagon’s center and at one of three alternating outer vertices, as shown. The small hexagons do not overlap.

Find the area of the shaded portion.

The three congruent small hexagons are shaded.

cm²
Optional scratch work

Section B — Extended response

Give a final answer and show your reasoning.

5 × 12 = 60 points
11

Recover the lower base of a trapezoid

Not answered

In trapezoid ABCD, the upper base AD is 12 cm and the height BD is 18 cm. Diagonal AC intersects BD at E, and

BE = 2DE.

Find the length of the lower base BC.

ADBCE AD = 12BD = 18BE = 2DE

BD is perpendicular to BC.

12

Complete two partial regions

Not answered

In parallelogram ABCD, BC = 10 cm. Triangle ECB is right-angled at C, with EC = 8 cm. Line BE meets AD at F, and EC meets AD at G.

The total shaded area is 10 cm² greater than Area(△EFG).

Find the area of parallelogram ABCD.

ABCDEFG BC = 10EC = 8

The shaded parts are △ABF and △GCD.

13

A nested midpoint-and-ratio chain

Not answered

Triangle ABC has area 180 cm². Point D is the midpoint of BC. Point E lies on AD with

AD = 3AE.

Point F lies on BE with EF = 3BF. Find the area of triangle AEF.

ABCDEF AD = 3AEEF = 3BF

D is the midpoint of BC.

14

Shaded regions in a square

Not answered

Square ABCD has side length 12. Point P is any point on AB.

Points M and N trisect BC; points I and H trisect AD. Points E, F, and G divide CD into four equal parts. The point orders are B–M–N–C, A–I–H–D, and C–E–F–G–D.

Find the total shaded area.

ABCDP GFE HINM

The shaded regions are quadrilateral DGPH and triangles FEP and MNP. P may be anywhere on AB.

15

Find the green quadrilateral

Not answered

F lies between A and D in rectangle ABCD. Segments BD and CF meet at E and divide the rectangle into four regions.

Triangle DEF (red) has area 4 cm², and triangle CDE (yellow) has area 6 cm².

Find the area of quadrilateral ABEF (green).

ABCDFE GreenRedYellow

The fourth region, triangle BEC, is unshaded.