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anonymous

  • 5 years ago

The ratio of the areas of two circles is 9 to 16. If the circumference of the larger circle is 20 cm, what is teh circumference of the smaller circle?

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  1. anonymous
    • 5 years ago
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    Are you familiar with cross multiplying? I belive you go 9/16 times (x/20cm) From there, working it out it becomes (20x9)/16 and that gave me 45/4cm or 11.25

  2. anonymous
    • 5 years ago
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    so answer is 11.25 cm?

  3. anonymous
    • 5 years ago
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    yeah thats what I got, still though do you know how to cross multiply?

  4. anonymous
    • 5 years ago
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    yes i noe, y?

  5. anonymous
    • 5 years ago
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    makes life much easier, just making sure because thats usuallly all you do when you have a ratio problem like this

  6. anonymous
    • 5 years ago
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    ok, but i just realized that the ratio given about the two circles is their area, not circumference!

  7. anonymous
    • 5 years ago
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    area=pi*r*r circumference is pi*2*r ratio of area of circle 1 to circle 2 is 9:16. 9/16=area1/area2=pi*r1*r1/pi*r2*r2=r1*r1/r2*r2=3*3/4*4 so, ratio of r is 3:4

  8. anonymous
    • 5 years ago
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    is teh answer 11.25 still correct then?

  9. anonymous
    • 5 years ago
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    lyam, sdo wat's the final answer?

  10. anonymous
    • 5 years ago
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    nope 3/4=X/20 4X=60 X=60/4=15 I think

  11. anonymous
    • 5 years ago
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    sorry i type slow

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