Math Is Fun Forum

paulb203

Member

Registered: 2023-02-24

Posts: 321

Estimation

A baby is born every 43 seconds in the UK in 2018

Work out an estimate for the total number of babies born in the UK in 2018

*

Is there more than one correct answer to these kind of quesitons?

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Bob

Administrator

Registered: 2010-06-20

Posts: 10,627

Re: Estimation

It sounds like you have to find out how many seconds in that year (not a leap year) and divide by 43.

But you also have to consider what variance there might be in making that assessment.  I'd certainly want to round off my answer ... decimal place figures after the point would have no meaning ... but even the whole number answer probably needs rounding further.  So two people could get different answers as a result of different amounts of rounding I suppose.  But all answers should be in the same ball park.  Someone must have known the total in order to get the 'every 43 seconds' claim.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

paulb203

Member

Registered: 2023-02-24

Posts: 321

Re: Estimation

Thanks, Bob.

It's from Maths Genie, GCSE Maths, Estimation.

Apparently when estimating (when you're not told how to round, specifically) we round each value to 1 significant figure.

I rounded the 43 to 40. Then, for an estimate of the seconds in the year, multiplied 60 by 60 by 20, 400, giving 28,800,000

then divided that by the 40 to get 720,000*

They also rounded the 43 to 40. And 24 to 20, and 365 to 400, but instead of multiplying 60 by 60 by 20 by 40, they mulitplied 60 by 60, and 20 by 400, to get 3600 and 8000 respectively. Then they rounded the 3600 to 4000, and multiplied that by 8000 to get 32,000,000

Then divided that by 40 to get 800,000

They did accept between 600,000 and 900,000 for the answer (which answers my original question; is there more than 1 answer for these questions).

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Prioritise. Persevere. No pain, no gain.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,627

Re: Estimation

If I've got to do this without a calculator then I'd do some carefully chosen rounding to make the sums easy.  But if I'm allowed then I'd always prefer to keep to the exact values until the end and only then round off.

365 x 24 x 60 x 60 / 43 is 733395.349 so the 'book' answer of 720000 is pretty good. I'd say 600000 to 800000 is reasonable.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

paulb203

Member

Registered: 2023-02-24

Posts: 321

Re: Estimation

Good point. Reminds me of teachers saying don't round as you go, round when you get the final answer. But I think this is different. I think THE POINT here is to show that you know how to round AS YOU GO. So the aim isn't accuracy, it's to show you know how to estimate each value to 1 sig fig, etc, as you go. I think.

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Prioritise. Persevere. No pain, no gain.