A regular pentagon has side length 12 cm. The perimeter of the pentagon is 60 cm and the area is 247.7 cm2. A second pentagon has side lengths that are one and a half times the first pentagon. Find the perimeter of the second pentagon.

Question

fibonaccichick666 · Answer

so, a pentagon has how many sides to start?

fionacndg · Answer

5

fionacndg · Answer

@FibonacciChick666

fibonaccichick666 · Answer

and how do we calculate perimeter?

anonymous · Answer

This is simple. 60*1.5=?

fionacndg · Answer

umm a+b+c... =perimeter of a pentagon @FibonacciChick666

fionacndg · Answer

40 @OrangeMaster

anonymous · Answer

No, it would be 90

fibonaccichick666 · Answer

yup, so now, we know each side is 1.5 times the old side.  So just add it up

fibonaccichick666 · Answer

@OrangeMaster , clearly they don't understand so why would you just give them the answer?

fionacndg · Answer

oops divided @OrangeMaster

anonymous · Answer

I didn't. I showed them how to do it. There is no need to do what you did.

fionacndg · Answer

@FibonacciChick666 13.5 each side?

fibonaccichick666 · Answer

You added, try times-ing.  (multiplication)

anonymous · Answer

60*1.5 is all you needed.

anonymous · Answer

Then to find the length of each side:$$90\div5=18$$

fibonaccichick666 · Answer

and it won't help because they don't understand the concept.  Yes you get the same answer, but concept wise is what I am going for

fionacndg · Answer

@FibonacciChick666 18

anonymous · Answer

This is the same concept, but much faster. He knows what the length of each side and the total length, but much faster.

fibonaccichick666 · Answer

yes good, so because it was a regular pentagon, that means that all of the sides have the same length, so now, what do you get for the perimeter?

fionacndg · Answer

ohhh @FibonacciChick666 90

anonymous · Answer

Perimeter: 90
Individual Side Length: 18

Are we good now?

fibonaccichick666 · Answer

yep, so as Orange pointed out you can do this another way:  because you could factor a 1.5 out of each term, you could just multiply by 1.5

anonymous · Answer

His way was also good. I guess everyone has their own way.

fionacndg · Answer

now I get this!! thanks so much! @OrangeMaster  @FibonacciChick666

fionacndg · Answer

I would have taken any help I can get

fibonaccichick666 · Answer

np

anonymous · Answer

same here

anonymous · Answer

Side scale of the 2 pentagon: 3/2
Perimeter of the small pentagon: 60
Perimeter of the big one: 60 x (3/2) = 90
Area of small pentagon: 247.7
Area of big one: (247.7) x (3/2)^2 = 247.7 x (9/4) = .....
Reminder: area scale is the square of side scale.