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Changing ratios, inverse variation and joint proportion
Free examples and worked answers. No account needed.
Practise the method.
Changing ratios, inverse variation and joint proportion
Changing ratios, inverse variation and joint proportion
Example 1
Red : blue counters =2:3. Adding 4 red counters changes the ratio to 3:3. How many blue counters were there?
Show worked answer
Answer: 12
- Write the original counts as 2t and 3t.
- 3t2t+4=33
- t=4, giving 12 blue counters.
Example 2
5 identical machines finish a job in 15 hours. At the same constant rate, how many machines finish it in 3 hours?
Show worked answer
Answer: 25
- Machine-hours stay constant: 5×15.
- Divide by 3 hours to get 25 machines.
Example 3
Red : blue counters =5:6. Adding 3 red counters changes the ratio to 6:6. How many blue counters were there?
Show worked answer
Answer: 18
- Write the original counts as 5t and 6t.
- 6t5t+3=66
- t=3, giving 18 blue counters.
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