Grade 7 Math — The unitary method
Find the value of one thing first, then scale it to any number — and tell direct proportion from inverse.
Name: ________________________
1.A store of food lasts 20 cows for 6 days. How long would the same store last 15 cows, in days?
2.Which of these pairs are in direct proportion?
- a) The number of taps filling a tank and the time it takes
- b) The number of pens bought and the total cost
- c) The number of workers and the days needed to finish a job
- d) The speed of a car and the time it takes on a fixed journey
3.A machine fills 350 bottles in 5 minutes. How many bottles does it fill in 8 minutes?
4.7 workers build a wall in 12 days. Working at the same rate, how long would 14 workers take, in days?
5.If 5 notebooks cost $150, what do 8 notebooks cost? Give just the number.
6.12 identical bricks weigh 30 lb. What do 20 of those bricks weigh, in pounds?
7.A car travels 240 miles in 4 hours. How far does it travel in 1 hour, in miles?
8.Sort each pair of quantities by the way they vary together.
Groups: Direct proportion · Inverse proportion
- Speed of a car and the time for a fixed journey
- Weight of rice bought and its cost
- Number of taps filling a tank and the time taken
- Number of workers and the days to finish a job
- Distance traveled and time taken at a steady speed
- Number of books bought and the total cost
Answer key — Grade 7 Math — The unitary method
- 1. 8
- 2. b) The number of pens bought and the total cost
- 3. 560
- 4. 6
- 5. 240
- 6. 50
- 7. 60
- 8. Number of books bought and the total cost → Direct proportion; Number of taps filling a tank and the time taken → Inverse proportion; Distance traveled and time taken at a steady speed → Direct proportion; Speed of a car and the time for a fixed journey → Inverse proportion; Number of workers and the days to finish a job → Inverse proportion; Weight of rice bought and its cost → Direct proportion