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Lesson plan Grade 4 Math

Foxglove Farm's Irrigation Gate: Two-Step Multiplication Problems

A grade 4 lesson where students multiply a two-digit flow rate by minutes, then by days, to find how many gallons an irrigation gate delivers to a farm field each week.

Objectives

  1. Students will multiply a two-digit flow rate by two-digit minutes to find gallons delivered in one watering session.
  2. Students will multiply a one-day total by a number of days to find a total amount for a multi-day schedule.

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: irrigation gate, area model, multistep problem

Teacher overview

At the fictional Foxglove Farm, a farmer opens an irrigation gate connected to a pump to water different fields. The gate releases a steady number of gallons every minute it stays open, so the farmer can predict exactly how much water a field receives by multiplying the flow rate by the minutes the gate is open, and then multiplying that daily amount by the number of days the schedule repeats. This lesson uses the irrigation gate to practice two-digit-by-two-digit multiplication and then a second multiplication step across several days. A common misconception in this lesson is that students find the gallons for one day correctly but then stop, treating that one-day total as if it already answers a question about a full week.

Procedure

Hook (5 min): Ask students how a farmer might know exactly how much water a field gets without measuring it directly. Explain that Foxglove Farm's irrigation gate releases the same number of gallons every minute, so the farmer can calculate the total instead of guessing.

Direct instruction (10 min): Model the worked example on the board. The gate releases 65 gallons of water every minute. If the farmer opens the gate for 24 minutes each morning to water one field, use an area model to multiply 65 × 24: split into 65 × 20 = 1,300 and 65 × 4 = 260, then add 1,300 + 260 = 1,560 gallons for one morning. Then explain that the farmer runs this same 24-minute watering for 6 mornings in a row, so the class multiplies 1,560 × 6 = 9,360 gallons for the whole week.

Guided practice (15 min): As a class, work through Question 1 on the handout together, a second field whose gate releases 48 gallons per minute while the farmer runs it for 32 minutes each day. Students first find the daily total (48 × 32 = 1,536 gallons), then multiply by 4 days (1,536 × 4 = 6,144 gallons). Ask a volunteer to explain out loud why the second multiplication step is necessary and what it represents.

Independent practice (10 min): Students complete Questions 2 and 3 on the handout without teacher help. Question 2 covers Field C, whose gate releases 54 gallons per minute for 28 minutes each day, run for 3 days. Question 3 covers Field D, whose gate releases 72 gallons per minute for 15 minutes each day, run for a full 7-day week.

Closure / exit ticket (10 min): On an index card, students solve Question 4 from the handout: a gate releases 39 gallons per minute for 26 minutes on a single day. How many gallons does the field receive that day? Collect the cards and check whether students used the area model or an equivalent strategy correctly before dismissal.

Foxglove Farm's Irrigation Gate: Two-Step Multiplication Problems — Grade 4 Math
Name: ____________________________ Date: ______________

Student Handout

Solve each problem. Multiply the flow rate, the gallons the gate releases each minute, by the number of minutes the gate is open to find the gallons for one day. When a problem covers more than one day, multiply that daily total by the number of days. Show your work with an area model or another strategy you have practiced.

  1. Foxglove Farm's second field has a gate that releases 48 gallons of water each minute. The farmer opens the gate for 32 minutes every day and runs this same watering for 4 days. How many gallons does the field receive over the 4 days?

  2. Field C has a gate that releases 54 gallons of water each minute. The farmer opens the gate for 28 minutes every day and runs it for 3 days. How many gallons does Field C receive over the 3 days?

  3. Field D has a gate that releases 72 gallons of water each minute. The farmer opens the gate for 15 minutes every day and runs it every day for a full 7-day week. How many gallons does Field D receive over the week?

  4. A gate releases 39 gallons of water each minute. The farmer opens the gate for 26 minutes on a single day. How many gallons does the field receive that day?

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: 6,144 gallons.
    Question 1, Foxglove Farm's second field: 48 gallons per minute × 32 minutes = 1,536 gallons in one day. 1,536 × 4 days = 6,144 gallons over the 4-day schedule.

  2. Answer: 4,536 gallons.
    Question 2, Field C: 54 gallons per minute × 28 minutes = 1,512 gallons in one day. 1,512 × 3 days = 4,536 gallons over 3 days.

  3. Answer: 7,560 gallons.
    Question 3, Field D: 72 gallons per minute × 15 minutes = 1,080 gallons in one day. 1,080 × 7 days = 7,560 gallons over the full week.

  4. Answer: 1,014 gallons.
    Question 4, exit ticket: 39 gallons per minute × 26 minutes = 1,014 gallons for the single day (40 × 26 = 1,040, minus one group of 26, equals 1,014).

Differentiation

Support (below grade level)

Provide a printed area-model template with the tens and ones already split apart (for example, boxes labeled "60" and "5" for a rate of 65) so students only need to fill in the four partial products and add them. Allow a calculator to check the final multiplication after showing work by hand.

Extension (above grade level)

Ask students to work backward: if a field received 3,060 gallons over 5 identical days, what was the daily total, and if the gate ran for 34 minutes each day, what was the flow rate in gallons per minute? Have students show every step of their reasoning.

ELL supports

Pre-teach "flow rate," "gate," and "schedule" using a labeled diagram of an irrigation gate with an arrow showing water moving into a field over time. Provide a sentence frame for the exit ticket: "The field received ___ gallons because the gate released ___ gallons each minute for ___ minutes."