It depends on what you are trying to calculate but the most common way I go to find percentage is to multiply by the number in decimal for ie. 50% = .5.
If you are looking for a way to do it quickly in your head I always take find out what 10% is like in the case of 100 it would be 10 so if I want to find 15% I know I can find 10% and if I cut what 10% is in half I will find 5% so likewise if I add what 10%+5% I will end up with 15%. For example, 10% of 100 is 10 half of 10 is 5 and 10+5 equals 15. If you need to find something like 20% or 30% I know that I can find 10% and instead of dividing(cutting it in half) I can multiply by 2 or 3. 10% + 10% =20%
I hope it helps, if you have more questions let me know!
Answer:
d1=-1/2,d2=1/2
Step-by-step explanation:
hope this helps
Question 2
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Formula
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Volume of the cylinder = πr²h
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Find Radius
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Radius = Diameter ÷ 2
Radius = 10 ÷ 2
Radius = 5 ft
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Find Volume
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Volume = πr²h
Volume = 3.14 x 5² x 21
Volume = 1648.5 ft³
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Answer: Volume = 1648.5 ft³
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Question 3
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Formula
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Volume of a sphere = 4/3πr³
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Find Volume
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Volume = 4/3 x 3.14 x 20³
Volume = 33493.3 ft³ (nearest tenth)
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Answer: Volume = 33493.3 ft³
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Subtract 2.2 from 7 and that will be equal to w
