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Math problem set Grade 3 Math

Pikeview Hydrant Flush Day: A Grade 3 Liters and Two-Step Set

A grade 3 problem set following one spring hydrant flushing day in a fictional town, with equal-groups liter totals, a truck tank, and two-step comparisons.

Objectives

  1. Students will multiply to find a total volume in liters from a number of equal groups.
  2. Students will solve two-step problems that combine multiplication with subtraction.
  3. Students will compare two equal-groups totals and justify which is larger.

Vocabulary

Key words: hydrant, flush, liter, equal groups, tank

Teacher overview

Each spring, many water utilities open their fire hydrants one at a time and let water run for a while, which pushes rust and settled grit out of the pipes before it can reach anyone's tap. Pikeview is a fictional town, and every liter total in this set was chosen for the mathematics rather than measured on a real flushing day. A real hydrant releases far more water, often thousands of liters in a single minute, so the amounts here are kept small to fit grade 3 numbers. The problems follow one crew through a single day, so the total found in problem 3 is the amount the crew accounts for in problem 4 and adds to again in problem 10, and the comparison in problem 8 returns to the two totals found at the start. The misconception this set is built to correct is the assumption that one number alone, either the count of hydrants or the liters from each hydrant, decides which street sends out more water in all, which leads students to answer problem 8 without multiplying either side. The larger amount from each Elm Street hydrant is the trap in problem 8, and the Extension asks for a street with fewer hydrants that sends out more water.

Pikeview Hydrant Flush Day: A Grade 3 Liters and Two-Step Set — Grade 3 Math
Name: ____________________________ Date: ______________

Problems

A crew in Pikeview flushes fire hydrants. Flushing means opening a hydrant and letting water run.

  1. The crew flushes 3 hydrants on Elm Street. Each hydrant sends out 60 liters. How many liters is that in all?
  2. The crew then flushes 5 hydrants on Ash Street. Each hydrant sends out 40 liters. How many liters is that in all?
  3. Add your answers from problems 1 and 2. How many liters has the crew flushed so far?
  4. The crew's truck carries a catch tank that holds 500 liters. The crew has put 380 liters of flush water into it. How many more liters can the catch tank still hold?
  5. A second crew flushes 4 hydrants. Each hydrant sends out 70 liters. Then 90 liters soak into a garden. How many liters run down the street?
  6. Pikeview has 8 blocks. Each block has 3 hydrants. How many hydrants does the town have in all?
  7. The crew splits the 24 hydrants into 4 equal groups, one group for each morning. How many hydrants are in each group?
  8. A worker says the 3 hydrants on Elm Street sent out more water than the 5 hydrants on Ash Street. Is the worker right? Show how you know.
  9. The crew flushes 2 more hydrants after lunch. Each one sends out 50 liters. How many liters is that in all?
  10. Add your answer from problem 9 to the 380 liters from problem 3. How many liters did this crew flush in the morning and after lunch together?

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: 180 liters.
    Three equal groups of 60 liters, so 3 × 60 = 180 liters.
  2. Answer: 200 liters.
    Five equal groups of 40 liters, so 5 × 40 = 200 liters.
  3. Answer: 380 liters.
    Add the two totals: 180 + 200 = 380 liters.
  4. Answer: 120 liters.
    Subtract what is already in the catch tank from what it holds: 500 − 380 = 120 more liters of room.
  5. Answer: 190 liters.
    Step one is 4 × 70 = 280 liters from the four hydrants. Step two is 280 − 90 = 190 liters running down the street. As an equation, 4 × 70 − 90 = n, and n = 190.
  6. Answer: 24 hydrants.
    Eight equal groups of 3 hydrants, so 8 × 3 = 24 hydrants.
  7. Answer: 6 hydrants.
    Splitting 24 hydrants into 4 equal groups gives 24 ÷ 4 = 6 hydrants in each group.
  8. Answer: No.
    Elm Street sent out 3 × 60 = 180 liters and Ash Street sent out 5 × 40 = 200 liters, and 180 is less than 200, so Ash Street sent out more even though each Elm Street hydrant sent out more water (60 liters versus 40 liters).
  9. Answer: 100 liters.
    Two equal groups of 50 liters, so 2 × 50 = 100 liters.
  10. Answer: 480 liters.
    Add the afternoon total to the morning total: 380 + 100 = 480 liters for the morning and after lunch together.

Differentiation

Support

Provide an equal-groups mat with the stated number of circles already drawn for problems 1, 2, 6, and 9, so students place the group size into each circle and count or skip count the total. Give a two-box organizer labeled step one and step two for problem 5. Allow a printed multiplication chart for the facts involving 60, 40, and 70 so the arithmetic does not block the reasoning.

Extension

Ask students to find how many liters the crew would flush if every one of the town's 24 hydrants sent out 60 liters, and to explain how they could check that answer with a smaller calculation they already did. Have them write a new problem in which one street with fewer hydrants really does send out more water than another street, and state the two numbers that make it work.

ELL supports

Pre-teach "hydrant," "flush," "tank," and "soak" with a simple street drawing that shows a hydrant, a stream of water along the curb, and a truck with a tank. Provide the sentence frames "There are ___ hydrants. Each one sends out ___ liters. That is ___ liters in all." and "First I ___. Then I ___." for problem 5. Allow labeled drawings in place of written equations on problems 1 and 2.