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secondary 2 | Maths
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secondary 2 chevron_right Maths

How to do (a) and (b)?

Date Posted: 7 years ago
Views: 322

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Tham KY
Tham Ky's answer
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7 years ago
Wait sorry, where does 3/32 comes from?
And the formula is 1/3(pi)(r)^2h right? "3/32(pi)(r)^2h" has extra variables.
But I can understand 3/32(1200) though, basically 1200=(r)^2h,and multiplying by 3/32 means reducing cone P radius and height simultaneously to meet cone Q's size.
Tham KY
Tham KY
7 years ago
Constant put outside, 3/32 ( pi(r^2)h ),
Keep 3/32, sub pi(r^2)h from P, becomes
3/32 (1200)...
Tham KY
Tham KY
7 years ago
3/32 comes from 1/3 * (3/4)^2 * 1/2
= 1/3 * 9/16 * 1/2 = 3/32
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7 years ago
wow! I understood now! combining them together adds 1/3 and pi together from 3/32 with 1200. That's cool!
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7 years ago
sorry, for (b), how is 1/8 derived?
Tham KY
Tham KY
7 years ago
(1/2)^3 = 1/8
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7 years ago
Why cube root height? I thought height is in cm?
Tham KY
Tham KY
7 years ago
Question says cone Z is similar to cone P,
Using similar figure property,
Area ratio = (length ratio) ^2
Volume ratio = (length ratio) ^3

From similarity and congruence chapter.