## rebecca1233 2 years ago ] The radius of a circle is multiplied by 10. Its area is _____ times bigger than the original circle.

1. rebecca1233

@Mertsj Can you guide me please

2. rebecca1233

@mathteacher1729

3. Mertsj

Lets make two circles. Let the radius of the first one be 1 and the radius of the second one be 10.

4. rebecca1233

alright

5. Mertsj

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6. Mertsj

What is the area of the first circle? Just leave your answer in terms of pi.

7. Mertsj

What is the area of the second circle? Again, leave your answer in terms of pi.

8. rebecca1233

but thats not what its asking for so the answer is 10

9. Mertsj

No, sweetheart. Just answer my questions. I'm trying to help you understand so you don't have to do so much work on the next problem you have that is similar to this one.

10. rebecca1233

so the first one is 1

11. rebecca1233

wait do i just do 10*10 cause its 10 times bigger that will give me 100

12. Mertsj

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13. rebecca1233

3.14 (1)

14. Mertsj

What is the area of the second circle? Don't use 3.14. Just leave your answer in terms of pi

15. rebecca1233

10

16. rebecca1233

ii ( 10)

17. Mertsj

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18. rebecca1233

alright so what next

19. Mertsj

So do you see that to find how many times bigger the second circle is we should divide the area of the second circle by the area of the first circle?

20. rebecca1233

so the area of the first circle is 1

21. Mertsj

Please look at the drawing I made. For the little circle, it says A = what?

22. rebecca1233

pie

23. Mertsj

And the area of the big circle is what?

24. rebecca1233

100pie

25. Mertsj

And what is 100 pi divided by pi ?

26. rebecca1233

100 / 3.14

27. Mertsj

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28. rebecca1233

100

29. rebecca1233

when i divide a 100 by pie i get a decimal

30. Mertsj

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31. rebecca1233

it equals 100

32. Mertsj

Do you understand so far because here is the important part which will save you work in the future?

33. rebecca1233

yes. i get it :) Thanks. can you help me with a few more questions im stuck on

34. rebecca1233

35. Mertsj

Wait. I want to teach you the general principle of the problem we just did.

36. rebecca1233

oh ok

37. Mertsj

In finding the area of a circle, what do you do with the radius?

38. Mertsj

You square the radius don't you?

39. rebecca1233

yes

40. Mertsj

So, if we make the radius 10 times bigger and then square it, since 10 squared is 100, the new circle will be 100 times bigger. Do you understand that?

41. rebecca1233

yes