Maths question

#1
My daughter has just started high school and has come home with this question, amongst others.

"A large circular pane of glass has a perimeter of 219.8cm, calculate the area of the glass"?


Now it's been 25 years since I needed to use pi(stop laughing at the back).

To get the radius I need to divide the perimeter(circumference) by pi and then divide the diameter by 2, correct?

Then calculate the area by using the pi x r2(pi x radius x radius) correct?

I get an answer of- area = 3846.5.

According to my daughters friends rather stuck up school teacher mother, it's wrong.

Is it, I'd dearly love to tell her she was in fact wrong.

Sorry for boring you's but it's bugging me.
 
#2
3844.55076
 
#6
#7
The method's right but you must have typed it into the calculator wrong or something.

Answer 2 is also slightly off (rounding errors? 3.14 used for pi?)

Remember not to quote too many decimal places or significant figures!
 
#11
now you are just showing off and no one likes a smart alec
 
#14
Maybe it's this calculator or me but when I divide 219.8 by pi(3.14) I get 70?
 
#16
devilish said:
Maybe it's this calculator or me but when I divide 219.8 by pi(3.14) I get 70?
Correct. To 2 decimal places your answer maybe right.
But pi is normally done to 4 places or 3.1416
 
#17
eodmatt said:
3844.55076
Yes, unless he's being sneaky and means the surface area.
Probably not, if he hasn't given the thickness of the glass.
 
#19
LOL, not total surface area.

the kids have been told to do it by the 3.14 method, so I was right! I'll be glad to let her know. A level(higher) maths and obviously a degree in something to be a high school teacher and little old me who left school with fcuk all but the tuck shop money to join up is just about to p1sh on her chips!

Cheers peeps.
 
#20
devilish said:
A level(higher) maths and obviously a degree in something to be a high school teacher and little old me who left school with fcuk all but the tuck shop money to join up is just about to p1sh on her chips!
:lol: :lol:
 

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