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Math problem set Grade 2 Math

Filling Ironbridge's Park Tank: A Grade 2 Running-Total Problem Set

Grade 2 students track gallons pumped into a small park water tank hour by hour, adding and subtracting three-digit running totals within 1000 to reach a fill goal.

Objectives

  1. Students will add three-digit amounts to build a running total within 1000.
  2. Students will subtract to find how many more gallons are needed to reach a goal.
  3. Students will compare two hourly amounts and state the difference.

Vocabulary

Key words: running total, gallons, compare

Teacher overview

Ironbridge (a fictional town used for this problem set) is refilling the small water tank at its park after scheduled cleaning, and a pump adds water each hour until the tank reaches its goal. This set walks students through building a running total hour by hour, then checking how close that total is to the tank's 700-gallon goal. A common misconception in this set is adding only the newest hour's amount instead of adding it to the running total from the hours before, so problems 2 and 3 ask students to build directly on their own previous answer rather than starting over each time.

Filling Ironbridge's Park Tank: A Grade 2 Running-Total Problem Set — Grade 2 Math
Name: ____________________________ Date: ______________

Problems

  1. Ironbridge's park tank starts empty. Hour 1: the pump adds 120 gallons. Hour 2: it adds 145 more gallons. How many gallons are in the tank after Hour 2?
  2. Hour 3: the pump adds 130 more gallons. Use your answer to problem 1. How many gallons are in the tank now?
  3. Hour 4: the pump adds 160 more gallons. Use your answer to problem 2. How many gallons are in the tank now?
  4. The tank needs 700 gallons to be full. Use your answer to problem 3. How many more gallons are needed?
  5. Hour 5: the pump adds 145 gallons. Use your answer to problem 3. How many gallons are in the tank now?
  6. Hour 4 added more gallons than Hour 2. How many more?
  7. Which hour added the fewest gallons?
  8. Add up all five hours. What is the total number of gallons?

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: 265 gallons. 120 + 145 = 265.
  2. Answer: 395 gallons. 265 + 130 = 395.
  3. Answer: 555 gallons. 395 + 160 = 555.
  4. Answer: 145 more gallons. 700 minus 555 equals 145.
  5. Answer: 700 gallons. 555 + 145 = 700.
  6. Answer: 15 more gallons. 160 minus 145 equals 15.
  7. Answer: Hour 1. It added 120 gallons, fewer than Hour 2 (145), Hour 3 (130), Hour 4 (160), or Hour 5 (145).
  8. Answer: 700 gallons. 120 + 145 + 130 + 160 + 145 = 700.

Differentiation

Support

Provide a running-total chart with the first two rows already filled in (Hour 1's amount and the Hour 1 plus Hour 2 total), so students only need to continue adding each new hour onto the total.

Extension

Ask students to figure out how many gallons per hour a faster pump would need to add, using only 4 equal hours instead of 5, to reach the same 700-gallon goal, checking their answer by addition rather than division.

ELL supports

Pre-teach "running total" and "goal" with a simple visual of a jar filling a little at a time across five drawn steps. Provide a sentence starter for problems 1 through 5: "After Hour ___, the tank has ___ gallons."

Extensions

Have students build a simple table with two columns, Hour and Total, and fill it in as they solve problems 1 through 5, so the running total is visible in one place instead of scattered across separate answers. Ask them to circle the row where the tank first reaches or passes 500 gallons, and to explain how they found that row using the table.