Worksheet Grade 4 Math
Duncastle Dam Fish Ladder: Counting Fish and Shift Minutes
A grade 4 worksheet at a fictional dam's fish ladder, where students find elapsed shift minutes, walking distances, and fish counts, then interpret a remainder.
Objectives
- Students will find elapsed time in minutes across a volunteer shift that includes a break.
- Students will solve multistep problems about fish counts and distances walked at a dam.
- Students will explain how rainfall upstream in a watershed reaches a dam far below.
Vocabulary
- Fish ladder
- A series of water steps built beside a dam so migrating fish, like salmon, can swim past it. Fish leap or swim from pool to pool to reach the river above.
- 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.
- Watershed
- A watershed is all the land where rain that falls will drain to the same stream, river, or lake. Everyone lives in a watershed, no matter how far from the water they live.
Also: shift, elapsed time
Teacher overview
Duncastle Dam is a fictional dam on the Halberd River, and a fish ladder runs alongside it so that fish traveling upstream can climb past the wall in short steps. Volunteers sit at a counting window partway up the ladder and record every fish that swims by during their shift. This worksheet uses one weekend of that counting work for problems about elapsed time, distance walked, and totals across two days. A common error in item 10 is subtracting the lunch break twice, so ask students to mark only the two watching periods on a number line before they add.
Student Worksheet
The fish ladder has 12 steps. Each step lifts a fish 2 feet higher. How many feet higher is a fish after it climbs all 12 steps?
The counting window is open 4 hours each day. How many minutes is that?
A volunteer's shift starts at 8:15 in the morning and ends at 11:45 in the morning. How many minutes long is the shift?
Two volunteers each work a shift from 8:15 in the morning to 11:45 in the morning. How many minutes do the two of them watch in all?
The path beside the ladder is 96 feet long. A worker walks up the path and then back down it. How many feet does he walk?
On Saturday, 148 fish passed the window in the morning and 96 fish passed in the afternoon. How many fish passed on Saturday?
On Sunday, 187 fish passed the window. How many more fish passed on Saturday than on Sunday?
The volunteers write one card for each fish counted on Saturday and bundle the cards into packs of 6. Using your answer from item 6, how many full packs do the cards make?
Using your work from item 8, how many cards are left outside the full packs?
A volunteer watches from 9:30 in the morning until 12:00 noon. She stops for a 25-minute lunch. Then she watches from 12:25 until 2:00 in the afternoon. How many minutes does she spend watching?
Explain why the fish ladder is built as many small steps instead of one tall jump.
Rain falls on hills far above Duncastle Dam and drains into the Halberd River. Explain how that faraway rain can change the water in the fish ladder.
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: 24 feet.
Twelve steps lift 2 feet each, so 12 × 2 = 24 feet in all.Answer: 240 minutes.
One hour is 60 minutes, so 4 hours is 4 × 60 = 240 minutes.Answer: 210 minutes.
From 8:15 to 11:15 is 3 hours, which is 180 minutes. From 11:15 to 11:45 is 30 more minutes. Adding gives 180 + 30 = 210 minutes.Answer: 420 minutes.
Each shift is 210 minutes, so two shifts are 210 × 2 = 420 minutes.Answer: 192 feet.
Up the path is 96 feet and back down is another 96 feet, so 96 × 2 = 192 feet.Answer: 244 fish.
Morning and afternoon counts add to 148 + 96 = 244 fish.Answer: 57 fish.
Saturday's 244 fish minus Sunday's 187 fish gives 244 − 187 = 57 more fish on Saturday.Answer: 40 packs.
244 ÷ 6. Six goes into 244 forty times because 6 × 40 = 240, which leaves 4 cards. The volunteers finish 40 full packs.Answer: 4 cards.
The division in item 8 leaves a remainder of 4, and 4 cards are not enough to make another pack of 6.Answer: 245 minutes.
From 9:30 to 12:00 is 150 minutes. From 12:25 to 2:00 is 95 minutes, because 12:25 to 1:25 is 60 minutes and 1:25 to 2:00 is 35 more. The lunch break is not watching time, so the answer is 150 + 95 = 245 minutes.Answer: Small steps let a fish rest between short climbs, and most fish cannot leap the whole height of the dam at once.
Accept any answer that names short climbs, resting pools, or a height that is too tall to jump in one try.Answer: Rain that falls on the hills runs downhill into streams that join the Halberd River, so the river rises and more water flows through the ladder.
Accept any answer that traces water downhill from the hills into the river and then to the dam.
Differentiation
Support
Give students a printed clock face and a blank number line for items 3 and 10 so they can hop from hour to hour before counting the extra minutes. For item 8, provide counters they can group into sixes.
Extension
Ask students to design a shift schedule that keeps the counting window covered for all 240 minutes in item 2 using shifts of 80 minutes, and to state how many volunteers the plan needs.
ELL supports
Pre-teach "shift," "fish ladder," "pack," and "left over" with a labeled drawing of the stepped pools and a counting window. Provide the sentence frame: The shift lasts ___ minutes because it starts at ___ and ends at ___.
Extensions
Have students find the total number of fish counted across Saturday and Sunday, then write one sentence for the dam's newsletter reporting the weekend total in a way a neighbor could understand.