Perimeter and Area

Learn perimeter, triangle area.

Lesson 2 of 32 parts Practice Flashcards

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Perimeter

Objective: Explain perimeter, apply the stated method, and check its conditions.

Perimeter is the total boundary length of a plane figure. A rectangle has two sides of length l and two of width w, giving P=2(l+w). Use common length units and do not confuse the boundary with the region it encloses. Perimeter uses length units, not square units.

Formulas

$Prectangle=2(l+w)$

Worked examples

Try itA rectangle has length 7 cm and width 6 cm. Find its perimeter.Show answer

Step 1: Add all four side lengths. Step 2: Use P=2(l+w)=2(7+6). Step 3: P=26 cm.

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Perimeter

Objective: Explain perimeter, apply the stated method, and check its conditions.

Formulas

$Prectangle=2(l+w)$

Worked examples

Try itA rectangle has length 7 cm and width 6 cm. Find its perimeter.Show answer

Step 1: Add all four side lengths. Step 2: Use P=2(l+w)=2(7+6). Step 3: P=26 cm.

Triangle Area

Objective: Explain triangle area, apply the stated method, and check its conditions.

A triangle’s area is half the product of a chosen base and its perpendicular height. A slanted side is not automatically the height. Area measures the enclosed region in square units; convert lengths to consistent units before multiplying. The height must be perpendicular to the base.

Formulas

$A=bh/2$

Worked examples

Try itA triangle has base 7 cm and perpendicular height 6 cm. Find its area.Show answer

Step 1: Use A=bh/2. Step 2: Substitute (7)(6)/2. Step 3: A=21 cm².

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