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Classroom activity Grade 3 Math

Hazelford Pump House Shift Checks: A Grade 3 Time Relay

A 40-minute grade 3 relay where teams read clock cards from a fictional pump house shift log and find how many minutes each equipment check lasted.

Objectives

  1. Students will find the number of minutes between a start time and an end time.
  2. Students will add two time intervals given in minutes.
  3. Students will use a number line to show a time interval that crosses the hour.

Vocabulary

Key words: shift, pump house, interval, start time, end time

Teacher overview

A pump house holds the pumps that push drinking water out to a town's pipes, and the operator on shift walks around the building several times a day to check each machine, writing down the time the check starts and the time it ends. Hazelford in this activity is a fictional town, and every time on the cards was written for the game rather than copied from a real shift log. This is a relay for teams of four to six students: a runner takes one clock card from a station, works out how many minutes that check lasted, records the interval on the team sheet, and tags the next runner. The activity teaches the concept directly, because a runner cannot tag the next student until the interval on their card is written down, so every student measures at least one interval in minutes.

Activity Directions

Step 1, setup before class (5 min). Print four clock-face cards per team. Card 1 shows a start of 8:15 and an end of 8:40. Card 2 shows 9:05 to 9:35. Card 3 shows 10:20 to 11:05. Card 4 shows 2:40 to 3:20. Place each team's cards face down at a station across the room, and tape an open number line marked in five-minute steps to the wall beside each station.

Step 2, explain how the activity works (5 min). Tell the class that an operator at the Hazelford pump house records the start time and the end time of every equipment check. Model one card on the wall number line: hop from 8:15 to 8:30, which is 15 minutes, then hop to 8:40, which is 10 more, so the check lasted 25 minutes. Show students where that answer goes on the team sheet.

Step 3, first relay round (10 min). Teams line up. One runner at a time walks to the station, turns over the next card, uses the wall number line to find the interval, writes the number of minutes on the team sheet, and returns to tag the next runner. A round ends when a team has all four intervals written down.

Step 4, second relay round (10 min). Reshuffle the cards at each station and run the relay again with the roles rotated, so a student who ran card 1 now runs a different card. Teams try to finish faster than their first round without missing an interval.

Step 5, record (6 min). Students return to their seats and complete handout items 1 through 6 on their own, using their team sheet and a number line as needed.

Step 6, debrief (4 min). The relay ends once every team has completed both rounds and every student has finished the handout. Ask two closing questions aloud: which card was hardest to work out, and why a card that crosses from one hour to the next takes an extra step. Take one answer for each.

Hazelford Pump House Shift Checks: A Grade 3 Time Relay — Grade 3 Math
Name: ____________________________ Date: ______________

Student Handout

An operator at the Hazelford pump house writes down when each check starts and ends.

  1. A pump check starts at 8:15 and ends at 8:40. How many minutes long was the check?
  2. A pump check starts at 9:05 and ends at 9:35. How many minutes long was the check?
  3. A pump check starts at 10:20 and ends at 11:05. How many minutes long was the check?
  4. A pump check starts at 2:40 and ends at 3:20. How many minutes long was the check?
  5. One check lasted 25 minutes. The next check lasted 30 minutes. How many minutes did the two checks take in all?
  6. Two checks each lasted 30 minutes. A worker says the two checks took more than one hour. Is the worker right? Tell how you know.

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: 25 minutes.
    From 8:15 to 8:30 is 15 minutes, and from 8:30 to 8:40 is 10 more, so 15 + 10 = 25 minutes.
  2. Answer: 30 minutes.
    From 9:05 to 9:35 the minute hand moves from 5 to 35, so the check lasted 35 − 5 = 30 minutes.
  3. Answer: 45 minutes.
    From 10:20 to 11:00 is 40 minutes, and from 11:00 to 11:05 is 5 more, so 40 + 5 = 45 minutes.
  4. Answer: 40 minutes.
    From 2:40 to 3:00 is 20 minutes, and from 3:00 to 3:20 is 20 more, so 20 + 20 = 40 minutes.
  5. Answer: 55 minutes.
    Adding the two intervals gives 25 + 30 = 55 minutes.
  6. Answer: No.
    Two checks of 30 minutes each come to 30 + 30 = 60 minutes, and 60 minutes is exactly one hour, not more than one hour.

Differentiation

Support

Give these students a paper clock with movable hands so they can turn the minute hand from the start time to the end time and count the five-minute steps as they go. Mark the wall number line for cards 3 and 4 with the hour boundary already circled, so the two-hop structure is visible before they start. Allow a partner to run the relay alongside them for the first round.

Extension

Ask students to write a fifth card of their own whose check lasts exactly 50 minutes and crosses an hour boundary, then trade cards with a partner and solve. Have them order the four intervals from shortest to longest and find the difference in minutes between the longest and the shortest check.

ELL supports

Pre-teach "shift," "check," "start," and "end" with a simple two-clock picture labeled start on the left and end on the right. Post the sentence frame "The check started at ___ and ended at ___, so it lasted ___ minutes" and have teams say it aloud before writing. Let students show a hop on the number line instead of explaining in words during the debrief.