IGCSE/GCSE/O & A Level/IB/University Student Forum
Qualification => Subject Doubts => GCE O - Level => Math => Topic started by: rickyponting66 on September 26, 2009, 05:07:39 pm
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Q. The Volume if two spheres are 640cm3 and 270cm3 . Find the ratio of their diameters?
This is a question from "Area and Volume" and in most of this type of questions this formulae is used "v1/v2=(L1/L2)`3"...
Help Plz..
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okk..first find the diameter of the biger sphere
4/3 pi * r^3 = 640
r^3 = 640/4.18
r = cube root of (152.78) = 5.34
so diameter = 2 * 5.34 = 10.68
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same for the smaller one..
4/3 pi r^3 = 240
r^3 = 240/4.188 = 57.29
r = 3.85
so diameter= 2 * 3.85 = 7.7
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so the ratio = 10.68 / 7.7 = 1.3
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Your Answer is Wrong...
Its answer is 4:3 . But How?
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its correct...1.3 can be expressed as 4:3
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1.3:1 multiply both by 3 ==> which gives u . 4:3
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that's right
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told him so..
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but why would I multiply ratio with 3?
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but why would I multiply ratio with 3?
to remove the decimal....ratios are in whole numbers preferably
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I am still confused :( :( :( :( :(
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the ratios are 1.3:1....to remove the decimal point and make it a whole number you multiply it with the number which would result in a number closest to a whole number.....so that number is 3.
it gives u 3.99(1.3X3)....very close to four...and 1X3=3
hence ratio is 4:3
remember you are not changing the ratio....
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I have answered some questions you had posted earlier...tell me if they r right or not