A 6cm section of plastic water pipe has inner diameter of 12cm and outer diameter of 15cm. find the volume of the plastic pipe not the hollow interior to the nearest hundredth

The volume of the plastic pipe  is 141 cubic centimetre

Step-by-step explanation:

Given:

The Length of the plastic water pipe = 12 cm

The inner Diameter of the  plastic water pipe = 12 cm

The outer Diameter of the  plastic water pipe = 15 cm

To Find:

the volume of the plastic pipe not the hollow interior to the nearest hundredth = ?

Solution:

The volume of the plastic water pipe can be found by using the volume of the cylinder formula

The Volume of the cylinder  =

Where

r is the radius

h is the height

Radius r  

On substituting the values

The Volume of the cylinder  

=

=

=  141.37   cubic centimetre

= 141  cubic centimetre

step-by-step explanation:

30% of $420 is 0.30($420) = $126 and $420 + $126 = $546.

or, 130% of $420 is 1.3($420) = $546.

notice that this is not the $600 original list price with which we started.

why doesn't this work?

the method does not work because 30% of $420 is not the same amount as the 30% of $600. it may seem obvious when stated this way, but it is a very common error made on problems of this type. we cannot just use the same percent and get back to the original amount because we are taking that percent of a different value.

to work problems of this type correctly, it is generally best to write an equation for the situation and then solve.

example: since (100% – 30%)(original price) = (sale price)

70% of the   (original price) is $420.

0.7x   = 420

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x = 600

the original cost was $600.

we may also solve this problem using the two-step method. working the problem in two steps requires us to use more algebra skills. we have to know that x = 1x (identity property of multiplicationtext annotation indicator) and that 1x – 0.3x = 0.7x (subtracting like terms). then we solve the problem as follows:

(original price) – 30%(original price) = sale price

x – 0.3x = 420

0.7x = $420

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x = 600

the original cost was $600.  

note that with both of the above methods we do obtain the correct original amount.

example: after a 5% pay raise, hermione is earning $22,680 per year. what was she earning before the pay raise?

105% of (original salary) = current salary

1.05x = 22,680

equation image indicator

x = 21,600

hermione earned $21,600 per year before the pay raise.

this is an example so maybe you will get how to at least do it!