Lesson plan Grade 4 Math

Bricklow Dam's Power Log: Multiplying and Rounding Big Totals

A grade 4 lesson at a fictional hydropower dam where students multiply hourly output by hours run, then round four-digit totals for the daily report.

Grade: Grade 4
Subject: Math
Material: Lesson plan
Time: 50 min
Prep: Low prep
Materials: Printed student handout, Chart paper, Place-value charts through ten thousands, Index cards

Standards

4.NBT.B.5 Common Core Math

Multiply a whole number of up to four digits by a one-digit whole number, and multiply two two-digit numbers, using strategies based on place value and the properties of operations. Illustrate and explain the calculation by using equations, rectangular arrays, and/or area models.

How this material aligns: Handout questions 1, 3, and 5 multiply a four-digit hourly output by a one-digit number of hours and a two-digit rate by a two-digit number of hours.

All materials for 4.NBT.B.5 →

4.NBT.A.3 Common Core Math

Use place value understanding to round multi-digit whole numbers to any place.

How this material aligns: Questions 2, 4, and 6 ask students to round four-digit power totals to the nearest thousand and to the nearest hundred for the daily report.

All materials for 4.NBT.A.3 →

4.OA.A.3 Common Core Math

Solve multistep word problems posed with whole numbers and having whole-number answers using the four operations, including problems in which remainders must be interpreted. Represent these problems using equations with a letter standing for the unknown quantity. Assess the reasonableness of answers using mental computation and estimation strategies including rounding.

How this material aligns: Question 7 subtracts the small generator's daily total from the large generator's, using totals students found in questions 1 and 5, and question 8 asks whether the rounded figure is a reasonable one to report.

All materials for 4.OA.A.3 →

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This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-09-03.

Objectives

Students will multiply a four-digit hourly output by a one-digit number of hours using place-value strategies.
Students will round four-digit totals to the nearest thousand and to the nearest hundred.
Students will compare two generators' daily totals using subtraction and explain which rounded figure is reasonable to report.

Vocabulary

Dam: A strong wall built across a river to hold back water. Dams store water for people and farms, help prevent floods, and can make electricity.
Hydropower: Electricity made from moving water, usually water falling through a dam. It is a renewable power source that can start up quickly when the electric grid needs it.

Also: generator, round, place value

Teacher overview

Bricklow Dam is a fictional dam on the Corbrook River that holds back a reservoir and sends part of the flow through machines called generators, which turn moving water into electricity measured in kilowatt-hours. Each morning the plant operator fills in a power log and reports the previous day's totals to the utility office, which prints rounded figures rather than exact ones. The misconception this lesson is built to correct is the idea that rounding means deleting the digits at the end, so that a student rounds 8,700 to the nearest thousand and writes 8,000 because the thousands digit "stays the same." The place-value work in this lesson keeps returning students to the one digit that decides the rounding.

Procedure

Hook (5 min): Ask students where a town's electricity comes from and take three or four answers. Explain that at Bricklow Dam, water falling through the dam spins generators, and that the operator keeps a written log of how much electricity each generator made and for how long. Write "kilowatt-hour" on the board as the unit that counts the electricity.

Direct instruction (12 min): Put the scenario numbers on chart paper. At Bricklow Dam, one large generator makes 1,450 kilowatt-hours every hour it runs. Model 1,450 times 6 by place value: 1,000 times 6 is 6,000, 400 times 6 is 2,400, 50 times 6 is 300, and adding those gives 8,700. Then draw a number line from 8,000 to 9,000 marked at the halfway point of 8,500, place 8,700 on it, and show that it sits closer to 9,000. Write the rule the class will use: look at the digit to the right of the place you are rounding to.

Guided practice (13 min): Work a second pair of problems together. All three of the dam's large generators run for one hour, each making 1,450 kilowatt-hours, so the class multiplies 1,450 by 3 and gets 4,350. Then place 4,350 on a number line from 4,000 to 5,000 and ask students to vote with thumbs up or down on whether it rounds to 4,000. If more than a quarter of the class votes for 5,000, draw the halfway mark at 4,500 again before moving on.

Independent practice (15 min): Students complete the eight questions on the student handout. Circulate and ask individual students to point to the digit that decided each rounding before they write the rounded number.

Closure / exit ticket (5 min): On an index card, each student rounds 6,481 kilowatt-hours to the nearest thousand and writes the digit they looked at to decide. Collect the cards and check for students who answered 7,000, which usually means they rounded up from the tens place first and then rounded a second time.

Bricklow Dam's Power Log: Multiplying and Rounding Big Totals — Grade 4 Math

Name: ____________________________ Date: ______________

Student Handout

Bricklow Dam keeps a power log. Use the numbers given in each question.

One large generator at Bricklow Dam makes 1,450 kilowatt-hours every hour. How many kilowatt-hours does it make in 6 hours?
Round 8,700 kilowatt-hours to the nearest thousand.
Bricklow Dam has 3 large generators. Each one makes 1,450 kilowatt-hours in an hour. How many kilowatt-hours do all 3 make in one hour?
Round 4,350 kilowatt-hours to the nearest thousand.
A small generator at the dam makes 65 kilowatt-hours every hour. How many kilowatt-hours does it make in 24 hours?
Round 1,560 kilowatt-hours to the nearest hundred.
On Monday the large generator made 8,700 kilowatt-hours and the small generator made 1,560 kilowatt-hours. How many more kilowatt-hours did the large generator make?
The operator reports about 9,000 kilowatt-hours instead of the exact 8,700. Explain in one or two sentences why a rounded number is useful in a report.

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: 8,700 kilowatt-hours.
Multiply 1,450 by 6 using place value: 1,000 times 6 equals 6,000, 400 times 6 equals 2,400, and 50 times 6 equals 300. Adding 6,000 plus 2,400 plus 300 gives 8,700 kilowatt-hours.
Answer: 9,000 kilowatt-hours.
To round to the nearest thousand, look at the hundreds digit of 8,700, which is 7. Because 7 is 5 or greater, the thousands digit goes up from 8 to 9, giving 9,000 kilowatt-hours. On a number line, 8,700 sits past the halfway mark of 8,500.
Answer: 4,350 kilowatt-hours.
Multiply 1,450 by 3: 1,000 times 3 equals 3,000, 400 times 3 equals 1,200, and 50 times 3 equals 150. Adding 3,000 plus 1,200 plus 150 gives 4,350 kilowatt-hours.
Answer: 4,000 kilowatt-hours.
Look at the hundreds digit of 4,350, which is 3. Because 3 is less than 5, the thousands digit stays 4 and the rest become zeros, giving 4,000 kilowatt-hours.
Answer: 1,560 kilowatt-hours.
Multiply 65 by 24 in two parts: 65 times 20 equals 1,300 and 65 times 4 equals 260. Adding 1,300 plus 260 gives 1,560 kilowatt-hours.
Answer: 1,600 kilowatt-hours.
To round to the nearest hundred, look at the tens digit of 1,560, which is 6. Because 6 is 5 or greater, the hundreds digit goes up from 5 to 6, giving 1,600 kilowatt-hours.
Answer: 7,140 kilowatt-hours.
Subtract the small generator's total from the large generator's total: 8,700 minus 1,560. Take away 1,000 to reach 7,700, then 500 to reach 7,200, then 60 to reach 7,140 kilowatt-hours.
Answer: A rounded number is easier to read and compare.
Accept any explanation stating that a rounded figure gives the size of the day's output at a glance and can be compared quickly with other days, while the exact count still stays in the operator's log for anyone who needs it.

Differentiation

Support (below grade level)

Provide a place-value chart with columns labeled through ten thousands and let students write each number into the chart before rounding, circling the deciding digit in colored pencil. For the multiplication items, supply an area model already drawn and partly labeled, with 1,000, 400, and 50 written along one side. Reduce the assignment to questions 1, 2, 3, and 4.

Extension (above grade level)

Ask students to build a five-day power log for the fictional Bricklow Dam in which the large generator runs a different whole number of hours each day, then report each day's exact total, each day's total rounded to the nearest thousand, and the five-day exact total. Students should then explain in writing whether adding the five rounded numbers gives the same result as rounding the exact five-day total, and why.

ELL supports

Pre-teach "generator," "round," and "report" using a labeled cross-section drawing of a dam with water flowing through a turbine and an arrow to a meter. Post a rounding number line from 8,000 to 9,000 with 8,500 marked and labeled "halfway." Provide sentence frames for questions 2 and 8: "I looked at the ___ digit, which is ___, so the answer is ___," and "A rounded number helps because ___."

Extensions

Students can compare the fictional Bricklow log with a real utility's published monthly generation summary, noting which place value the utility chose to round to and why that choice fits the size of the numbers being reported. A follow-up discussion can connect the operator's daily log to the careers that keep a hydroelectric station running, including operators, mechanics, and the engineers who schedule releases from the reservoir.