Need to know area of a circle?
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silverysea
- Posts: 1105
- Joined: Fri Mar 04, 2011 3:32 pm
Need to know area of a circle?
For superselective, do they need to be able to calculate the area of a circle? Tutor did this today but I've not seen it in any test papers tried so far.
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leanmeamum
- Posts: 736
- Joined: Sat Dec 03, 2011 4:14 pm
Re: Need to know area of a circle?
they give the formula for the area of a circle or the area, if there is a question involving it.
Maybe the tutor covered the topic just to show how it works so it is easy for the child
to see understand circles
Maybe the tutor covered the topic just to show how it works so it is easy for the child
to see understand circles
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silverysea
- Posts: 1105
- Joined: Fri Mar 04, 2011 3:32 pm
Re: Need to know area of a circle?
Ok that does help! It's all about familiarity I guess!
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parent2013
- Posts: 452
- Joined: Mon Aug 12, 2013 10:13 am
Re: Need to know area of a circle?
The answer unfortunately is "Yes" for superselectives. I have seen numerous examples in private school papers from previous years where this concept has been tested. It is not rocket science and there are only 2 formulas to remember.
Circumference : 2 X Pi X Radius (where Pi is 3.14 or 3 for approximation)
OR Pi X Diameter (as Diameter is twice the radius)
Area: Pi X (square of radius)
One example I remember from top of the head is:
1. Ben has a bicycle with a wheel of radius 1m, how much distance it covers in 10 turns
Using Pi = 3, the distance in one turn is the circumference i.e. 2 X 3 X 1 = 6m. Therefore in 10 turns, it will cover a distance of 10 X 6m i.e. 60m.
2. His grandfather "John" has a bicycle with a bigger wheel of radius 1.5m, how much additional distance it covers in 10 turns?
Using Pi = 3, the distance in one turn is the circumference i.e. 2 X 3 X 1.5 = 9m. Therefore in 10 turns, it will cover a distance of 10 X 6m i.e. 90m. The answer is "additional" distance i.e. 90-60 = 30m.
Circumference : 2 X Pi X Radius (where Pi is 3.14 or 3 for approximation)
OR Pi X Diameter (as Diameter is twice the radius)
Area: Pi X (square of radius)
One example I remember from top of the head is:
1. Ben has a bicycle with a wheel of radius 1m, how much distance it covers in 10 turns
Using Pi = 3, the distance in one turn is the circumference i.e. 2 X 3 X 1 = 6m. Therefore in 10 turns, it will cover a distance of 10 X 6m i.e. 60m.
2. His grandfather "John" has a bicycle with a bigger wheel of radius 1.5m, how much additional distance it covers in 10 turns?
Using Pi = 3, the distance in one turn is the circumference i.e. 2 X 3 X 1.5 = 9m. Therefore in 10 turns, it will cover a distance of 10 X 6m i.e. 90m. The answer is "additional" distance i.e. 90-60 = 30m.
