Lesson plan Grade 6 Math
Ridgemont Plant's Daily Output: Converting Million Gallons a Day
A grade 6 math lesson where students convert a fictional treatment plant's daily output from million gallons per day into gallons per day and gallons per minute.
Objectives
- Students will convert a treatment plant's daily output from million gallons per day (MGD) to gallons per day.
- Students will use a standard conversion rate to convert MGD to gallons per minute.
- Students will explain why a plant's water production must be described with a time unit attached.
Vocabulary
- Flow rate
- Flow rate measures how much water moves past a point in a certain amount of time, like gallons per minute through a garden hose. Bigger pipes and stronger pushes give bigger flow rates.
Also: MGD, conversion factor
Teacher overview
Water treatment plants report how much water they produce using million gallons per day, written MGD, the standard unit operators use nationwide. This lesson has students convert a single MGD figure into gallons per day and into gallons per minute, using the standard conversion that one MGD equals about 694 gallons per minute, giving students a concrete single-step unit-rate conversion instead of an abstract one.
A common misconception is treating "MGD" as if it already told you the rate in gallons per minute or per day, without doing any conversion. The lesson's hook is built to surface that confusion before direct instruction begins.
Procedure
Hook (5 min): Tell students that Ridgemont Water Treatment Plant (a fictional plant used for this lesson) produces 2.4 MGD on an average day. Ask: "Is that a lot of water? How many gallons is that, really?" Collect a few guesses on the board without correcting them yet.
Direct instruction (10 min): Explain that MGD stands for million gallons per day, so 1 MGD equals 1,000,000 gallons per day. Model converting Ridgemont's 2.4 MGD: 2.4 × 1,000,000 = 2,400,000 gallons per day. Then introduce the standard conversion that operators use to describe flow by the minute: 1 MGD equals about 694 gallons per minute. Model: 2.4 × 694 = 1,665.6, which rounds to about 1,666 gallons per minute.
Guided practice (15 min): In pairs, students convert a second fictional plant's output. Elm Fork Plant treats 1.8 MGD. Students find gallons per day (1.8 × 1,000,000 = 1,800,000) and gallons per minute (1.8 × 694 = 1,249.2, which rounds to about 1,249). Circulate and check that pairs are multiplying by the correct conversion factor for each unit.
Independent practice (10 min): Each student completes two conversions on the handout for a third fictional plant, Sable Hollow Plant, which treats 3.5 MGD:
- Gallons per day
- Gallons per minute
Closure / exit ticket (5 min): Students answer one question on an index card: "A plant treats exactly 1 MGD. About how many gallons per minute is that?" Collect and scan for the correct use of the 694 gallons-per-minute conversion rate 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
Answer: 3,500,000 gallons per day.
3.5 MGD × 1,000,000 gallons per MGD = 3,500,000 gallons per day.Answer: 2,429 gallons per minute.
3.5 MGD × 694 gallons per minute per MGD = 2,429 gallons per minute.Exit ticket answer: 694 gallons per minute.
A plant treating exactly 1 MGD converts using the same standard rate: 1 × 694 = 694 gallons per minute.
Differentiation
Support (below grade level)
Provide a labeled conversion card: "MGD → gallons per day: multiply by 1,000,000" and "MGD → gallons per minute: multiply by 694," and allow a calculator for every multiplication. Reduce independent practice to the gallons-per-day conversion only, saving gallons per minute for guided review.
Extension (above grade level)
Ask students to find how many gallons the fictional Sable Hollow Plant (3.5 MGD) produces in one hour, starting from their gallons-per-minute answer, and to explain which of the three units (per day, per minute, per hour) would be most useful for a plant operator checking on the plant every half hour.
ELL supports
Pre-teach "MGD," "conversion factor," and "flow rate" with a simple visual showing a water tank filling over a full day, labeled with all three units side by side. Allow students to show their multiplication steps with numbers alone, without a written explanation, for the guided and independent practice problems.