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We were sent in a few ideas about this task. Oliver from Coddington C of E Primary School in England explained which calculations looked easiest and hardest:
I think that Gothenburg will be the easiest because you are only taking off the one and the zero, which is relatively easy.
I think Launceston is the hardest one to work out because it is the biggest number and the biggest calculation.
Fin from Springvale Primary in England thought about subtracting 100km from each distance as well as 1000km:
We noticed that when you travelled 1000 km in, the only digit that changed was the thousands digit and it went down by one. We also tried the hundreds column. Launceston was hard because it had a ten thousand column. When we did the hundreds Gothenburg was hard because the hundreds column was a zero so we had to use the thousands column too.
When we added the extra distance the same thing happened but the digit went up not down.
Joe from Millhouse Primary in England also had similar ideas, and wrote some new questions:
I noticed that it was easy because it was just taking one away from the thousands column.
The easiest was Istanbul because everyone can do 2-1.
I recognised Launceston was the hardest because it isn't just taking one away from the first column it is taking away from the second.
Here are some examples of similar questions I came up with:
If I was travelling to Launceston and someone took me 10,000km how many km would there be left with?
If I was traveling to Istanbul and somebody took me 2,000km how many would I have left?
We also thought if someone had taken us 100km away you take away one from the hundreds column.
Thank you all for sharing your thoughts with us!