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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
Optional enrichment: Changing ratios, inverse variation and joint proportion
Example 1
Light intensity I is inversely proportional to the square of distance d. At d=6m,I=54. Find I at d=18m.
Show worked answer
Answer: 6
- Tripling distance divides intensity by 32=9.
- The new intensity is 6.
Example 2
y is proportional to zx2. When x=2,z=2,y=20. Find y when x=4 and z=6. Give an exact fraction if needed.
Show worked answer
Answer: 380
- Doubling x multiplies y by 4;
- tripling z divides it by 3.
- Apply 34 to 20.
Example 3
Light intensity I is inversely proportional to the square of distance d. At d=6m,I=54. Find I at d=18m.
Show worked answer
Answer: 6
- Tripling distance divides intensity by 32=9.
- The new intensity is 6.
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