In the next section, formal methods are used for calculating perimeter, area and volume; however, it is always important to have a method for checking how sensible an answer is. The following two sub-sections outline methods for estimating lengths, distances, area and volume.
Body measurements that could be used to estimate basic lengths and distances.
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Indigenous methods of measurement |
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Measurement |
Description |
Approximate length |
|
Cubit |
From the tip of the outstretched hand to the elbow. |
ψ m (actually 47 cm) |
|
Hand |
The width across all 5 fingers of the hand. |
10 cm |
|
Digit |
The width across the knuckle of the middle finger. |
2 cm |
|
Pace |
One good-sized step. |
1 m (actually 90 cm) |
|
Foot |
The length of an average foot. |
30 cm |
There are also other common measurements that most people are familiar with that can be used to check how sensible an answer is.
EXAMPLE:
A standard soccer pitch can have the following dimensions:
Standard soccer field
Answer: 100 m + 80 m + 100 m + 80 m = 360 m
- A learner was asked to calculate the length of fencing around the perimeter of his school and his answer was 250 m. Referring to the dimensions of the soccer pitch, does this answer make sense?
Answer: No this does not make sense. A soccer pitch has a total perimeter of 360 m and his answer is smaller than this. It would have to be a really small school for this to be true.
Measuring Area and Volume
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Area refers to two dimensions being multiplied by each other. |
weeeeeeeeeee | Volume refers to three dimensions multiplied together. |
The previous measurement estimates can be used to estimate area and volume as well:
EXAMPLE:
Is it incorrect to estimate the area of the ceiling of a normal classroom to be 10 m2?
Answer: Yes, it is incorrect. Even a small classroom would be approximately 4 paces by 5 paces. This would be an area of 20 m2.