Year 7 has been very busy in term two doing things like school camps and NAPLAN.
Now we are back with our full weeks of math and looking at patterns in the real world.

Today we looked at the growth rate of babies in their first 13 weeks.

The WHO provides the data - we used every two weeks to develop models for predicting - interpolating and extrapolating. This way we could check our maths with the real data!

We used tables, graphs and developing algebraic rules to make predictions and compared their results. Alex pointed out how ridiculous it would be to keep using our models into teenage years to illustrate how extrapolation can be unreliable. Here are some notes from today and Alex's example:

**How reliable are our models?**

Reasonably reliable for interpolating.

Not as reliable for extrapolating. Remember Alex calculated the weight of a 13 year old at the same growth rate as babies in their first 13 weeks.

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**13 years = 13 x 52 weeks**

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**13 years = 676 weeks**

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Our formula/equation/rule

Let t = time weeks and k = weight in kg

k = 0.25 x t + 3.3

for 13 years old

k = 0.25 x 676 + 3.3

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k = 172.3 kg

That's not average in any country for a 13 year old boy!

The CDC, in the USA, says the average weight for a male at 13 years old is **51.68229 kg **That's more than 100 kg lighter than our formula says.

Can you find the average weight of a 13 year old in another country?

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BABY BLUE WHALES

We talked about including units on our work to show kilograms otherwise our baby data could be in tonnes or even milligrams. A 3 tonne baby! Crazy!

... or not....? I did some searching....

For interest: Close to 3 tonnes are baby blue whales and their average difference is about 91 kg a day!!

Their formula would be** k = 91 x d + 3000** and reliable for 365 days!

where** k = weight in kilograms** and **d = time in days**. **3000 is the initial value** (or 2700 - see below).

After about a year inside its mother's womb, a baby blue whale emerges weighing up to 3 tons (2.7 metric tons) and stretching to 25 feet (8 meters). It gorges on nothing but mother's milk and gains **about 200 pounds**(91 kilograms) every day for its first year.

animals.nationalgeographic.com.au/animals/mammals/**blue**-**whale**/

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