Learn with Amar
Teaching video
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Grade 7 chapters and video availability01 · Read and understand
What you will learn
- Explain how to find a rate when both quantities are fractions.
- Solve the two practice problems and explain how the assumptions affect the answers.
Before you start
Divide fractions by multiplying by a reciprocal.
Keep paper nearby. Read the question once for the context, then again to identify what is known and what you need to find.
Start with a question
A model dispenser releases 3/4 litre in 2/5 minute at a constant rate. How many litres does it release per minute?
Why this math matters
Dividing two measured fractions gives the amount per one unit of the denominator quantity. Label the numerator and denominator before comparing flow rates or travel speeds.
Set up the model
A useful answer starts with clear assumptions:
- The release rate is constant.
- The requested rate is litres per minute, not minutes per litre.
02 · Work through the example
Follow the reasoning, one step at a time.
Try to predict the next step before reading it. After each calculation, explain why the operation makes sense and how it helps answer the original question.
Work through it with Amar
See this example unfold.
The complete worked example, one idea at a time.
Find a rate when both quantities are fractions
PausedQuestion: Start with the question. Paused.
Question
Start with the question
A model dispenser releases 3/4 litre in 2/5 minute at a constant rate. How many litres does it release per minute?
Before you calculate
Read what is known and what you need to find. Make a prediction before moving to the first calculation.
Starts paused. Play advances through the full text at a reading pace; pause whenever you need more time. Previous, Next, and the phase buttons let you set your own pace. Playback pauses when this walkthrough leaves the screen or you switch tabs.
Your device’s reduced-motion setting keeps each phase still. Manual controls remain available. The full written solution stays below.
Represent the quantities
rate = (3/4 L)/(2/5 min)
Place the quantity being measured over the time to identify the requested units.
Apply the relationship
(3/4) × (5/2) = 15/8
Dividing by two fifths scales the output to a full minute.
Check and interpret
15/8 = 1.875 L/min; (15/8)(2/5) = 3/4 L
Multiplying the rate by the original time recovers the original volume.
The result
15/8 = 1.875 L/min; (15/8)(2/5) = 3/4 L
Multiplying the rate by the original time recovers the original volume.
Common mistakes to catch
- Multiplying the original two fractions does not calculate a unit rate.
- Inverting the entire ratio would produce minutes per litre.
03 · Practice independently
Try it before revealing the answer.
Use paper or a calculator as needed. Write your units and reasoning, then open the hint or explanation to check your approach.
Practice 1
A walker covers 5/6 km in 1/3 hour. Find the constant speed.
Show a hint
Divide distance by time.
Reveal answer and explanation
2.5 km/h
(5/6) ÷ (1/3) = 5/2 kilometres per hour.
Practice 2
A pump supplies 7/4 L/min. How much does it supply in 2/7 minute?
Show a hint
Multiply the rate by the time.
Reveal answer and explanation
1/2 litre
(7/4)(2/7) = 1/2; minute units cancel.
Take the idea with you
Label the numerator and denominator before comparing flow rates or travel speeds.
04 · Reflect and continue
Can you explain it in your own words?
Before moving on, explain the main idea without looking at the worked example. Try both practice questions, check your reasoning, and name one mistake you now know how to avoid. Return to a step if you still need support.
Up next: Recover the constant of proportionality
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