Question

Where have you used addition of four-digit numbers? In what ways has it been helpful for you?​

Answer 1

Answer:

In this answer I presume that all digits 1,2,5,6 must be present in the number.

There are 4!=24 such numbers.

We can index them with i=1,…,24 and write each of them as

ni=ai+10bi+100ci+1000di

where {ai,bi,ci,di}={1,2,5,6}

Then

∑i=124ni=∑i=124ai+10∑i=124bi+100∑i=124ci+1000∑i=124di

{i∣ai=1}, {i∣ai=2}, {i∣ai=5} and {i∣ai=6} have equal cardinality 244=6 so:

∑i=124ai=6.1+6.2+6.5+6.6=6(1+2+5+6)=84

This can also be applied for b,c and d and finally we find:

∑i=124ni=84+10.84+100.84+1000.84=1111.84=93324

Does this really answers your question? If not, then please let me know.

Step-by-step explanation:

the following is the explanation ^_^

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Answer 2

Answer:

yeah in construction s and millimetres