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Lesson plan Grade 5 Careers & CTE

The Mossgrove Operator's Daily Log: A Grade 5 Decimal Lesson

A 45-minute grade 5 careers lesson where students act as trainee plant operators and add, subtract, and multiply decimals from a fictional daily log.

Objectives

  1. Students will add and subtract decimals to hundredths from a plant operator's log.
  2. Students will multiply a decimal by a whole number to find totals from the log.
  3. Students will explain what each answer means for the operator's work.

Vocabulary

Key words: operator, log, decimal, sample

Teacher overview

A treatment plant operator writes readings in a log all shift long, and those readings are decimals. This lesson lets students act as trainee operators at Mossgrove, a made-up plant, and work the decimal math the job actually uses. A common mistake in this lesson is not lining up the decimal points when adding or subtracting, which makes the answer far too large or too small; the procedure models that fix directly before students practice.

Procedure

Hook (5 min): Show a short pretend log line on the board: "Chlorine tank: 3.50 feet at noon." Ask why an operator would write a reading with a decimal instead of a round number. Take two or three answers about being exact.

Direct instruction (10 min): Model one worked example that is not on the handout. Write "Tank fell from 3.50 feet to 2.25 feet. How much was used?" Line up the decimal points and subtract: 3.50 minus 2.25 equals 1.25 feet. Then model a multiplication example: "3 bags at 4.5 pounds each." Multiply 4.5 by 3 to get 13.5 pounds, and show where the decimal point lands.

Guided practice (10 min): Work handout problem 1 together, lining up the decimals as a class. Then have pairs try problem 2 and share how they placed the decimal point in the product.

Independent practice (15 min): Students complete the rest of the daily-log handout on their own. Circulate and check that decimal points are lined up in the addition and subtraction problems.

Closure and formative check (5 min): Exit ticket. Each student solves one last log line on a card: "Powder on hand 20.0 pounds, used 5.5 pounds. How much is left?" Collect and scan for the correct answer of 14.5 pounds; reteach decimal lineup next session if more than a few miss it.

The Mossgrove Operator's Daily Log: A Grade 5 Decimal Lesson — Grade 5 Careers & CTE
Name: ____________________________ Date: ______________

Student Handout

You are a trainee operator at the Mossgrove plant, a made-up plant for this lesson. Read each log line and solve. Show your work.

  1. The chlorine tank started the shift at 6.75 feet deep and ended at 5.40 feet deep. How many feet of chlorine were used?
  2. Each bag of treatment powder weighs 12.5 pounds. The operator added 4 bags. How many pounds of powder is that?
  3. Filter 1 was cleaned in 8.5 minutes and Filter 2 in 7.25 minutes. How many minutes did both filters take together?
  4. Drum A holds 18.6 gallons of chemical and Drum B holds 12.75 gallons. How many gallons do the two drums hold together?
  5. The operator refilled a tank with 9 buckets, and each bucket held 4.5 gallons. How many gallons went into the tank?
  6. The operator made 6 sample checks, and each check took 2.5 minutes. How many minutes did all the checks take?
  7. The plant had 50.0 pounds of powder on hand and used 12.5 pounds today. How many pounds of powder are left?

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: 1.35 feet. Line up the decimals and subtract: 6.75 minus 5.40 equals 1.35 feet used.
  2. Answer: 50 pounds. Multiply 12.5 by 4: 12.5 times 4 equals 50.0, which is 50 pounds.
  3. Answer: 15.75 minutes. Line up the decimals and add: 8.5 plus 7.25 equals 15.75 minutes.
  4. Answer: 31.35 gallons. Add 18.6 plus 12.75 equals 31.35 gallons.
  5. Answer: 40.5 gallons. Multiply 4.5 by 9: 4.5 times 9 equals 40.5 gallons.
  6. Answer: 15 minutes. Multiply 2.5 by 6: 2.5 times 6 equals 15.0, which is 15 minutes.
  7. Answer: 37.5 pounds. Subtract 12.5 from 50.0: 50.0 minus 12.5 equals 37.5 pounds left.

Differentiation

Support

Give these students a handout with a decimal-point guide line printed under each addition and subtraction problem so the place values stay aligned. Allow a calculator for the multiplication problems, and start them on problems 1 and 3 before the multiplication items.

Extension

Ask students to write one new log line of their own that uses a decimal, trade with a partner, solve each other's line, and check that the decimal point lands in the right place.

ELL supports

Pre-teach "log," "decimal," "powder," and "drum" with a labeled picture for each. Provide a sentence frame for the written work: "The operator used ___ because ___." Allow answers to be shown as the number sentence plus the result rather than a full written explanation.