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Lesson plan Grade 5 Math

Ridgeline Fire Station's Backup Water Tank: A Grade 5 Volume Lesson

A 45-minute grade 5 lesson in which students find the volume of two rectangular water tank designs for a fictional fire station and convert cubic feet to gallons.

Objectives

  1. Students will calculate the volume of a rectangular prism using the formula V = l x w x h.
  2. Students will convert a volume in cubic feet to gallons using the conversion factor 7.48 gallons per cubic foot.
  3. Students will compare two tank designs to determine which one holds more water.

Vocabulary

Key words: volume, rectangular prism, cubic foot, conversion factor, capacity

Teacher overview

Ridgeline Fire Station, a fictional station used for this lesson, is adding a rectangular backup water tank to its equipment room in case the public water supply is interrupted during a fire response. Two possible tank designs fit the available space, and the department has asked a grade 5 class to help decide which design holds more water. This lesson uses the volume formula V = l x w x h to find each design's capacity, then converts the answer from cubic feet to gallons using the 7.48-gallons-per-cubic-foot conversion that appears on real tank specification sheets. A common misconception in this lesson is that a tank with one larger dimension automatically holds more water; the two designs are built so that neither option looks obviously larger by eye, which pushes students to multiply all three dimensions rather than compare them by sight.

Procedure

Hook (5 min): Show students the outlines of two rectangular boxes drawn to different proportions and labeled "Option A" and "Option B." Ask students to guess, without calculating, which box holds more water, and record the class's guesses on the board without comment.

Direct instruction (10 min): Introduce the volume formula V = l x w x h for a rectangular prism and work through Option A as a class: 8 feet long, 5 feet wide, and 4 feet deep. Model the multiplication step by step: 8 x 5 = 40, then 40 x 4 = 160 cubic feet. Introduce the conversion factor of 7.48 gallons per cubic foot and multiply 160 x 7.48 = 1,196.8 gallons.

Guided practice (15 min): In pairs, students calculate the volume of Option B: 6 feet long, 6 feet wide, and 5 feet deep. They find 6 x 6 = 36, then 36 x 5 = 180 cubic feet, then convert to gallons: 180 x 7.48 = 1,346.4 gallons. Circulate to check that pairs are multiplying all three dimensions rather than adding them.

Independent practice (10 min): Each student answers two numbered questions on the handout:

  1. Which option holds more water, and by how many gallons?
  2. A third design measures 10 feet long, 4 feet wide, and 3 feet deep. How many gallons would it hold?

Closure / exit ticket (5 min): Students answer question 3 on an index card:

  1. A tank measures 5 feet by 5 feet by 6 feet. What is its volume in cubic feet?

Collect the cards and scan for correct use of all three dimensions before dismissal.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: 149.6 gal.
    Option A: 8 x 5 x 4 = 160 cu ft; 160 x 7.48 = 1,196.8 gal. Option B: 6 x 6 x 5 = 180 cu ft; 180 x 7.48 = 1,346.4 gal. Option B holds more, and 1,346.4 minus 1,196.8 equals 149.6 gallons more.
  2. Answer: 897.6 gal.
    10 x 4 = 40; 40 x 3 = 120 cubic feet. 120 x 7.48 = 897.6 gallons.
  3. Answer: 150 cu ft.
    5 x 5 = 25; 25 x 6 = 150 cubic feet. This exit ticket stops at cubic feet and does not require the gallon conversion.

Differentiation

Support (below grade level)

Provide a partially completed multiplication chart showing 8 x 5 and 6 x 6 already calculated so students only need to complete the final multiplication step, and allow a calculator for every gallon conversion.

Extension (above grade level)

Ask students to design a fourth rectangular tank that holds more water than Option B while using no single dimension greater than 6 feet, then prove their design works by calculating its volume and gallon capacity.

ELL supports

Pre-teach "length," "width," "height," and "capacity" using a physical shoebox labeled on each side in English and, where possible, in students' home languages. Provide a sentence frame for independent practice: "Option ___ holds more water because its volume is ___ cubic feet."

Extensions

Have students measure a real box, bin, or classroom storage container in feet (or convert from inches), calculate its volume, and convert that volume to gallons to see how much water an object that size could hold.