Add new comment
-
Want facts and want them fast? Our Maths in a minute series explores key mathematical concepts in just a few words.
Here's our coverage from the International Congress of Mathematicians 2022, including the Fields Medals and other prizes.
The COVID-19 pandemic has amplified the differences between us. Understanding these inequalities is crucial for this and future pandemics.
Now it's the turn of mathematicians to help to improve the communities of the future.
There have been accusations that the modelling projecting the course of the pandemic was too pessimistic. Are they justified?
We all know what turbulence is, but nobody understands it.
If first number is 100a + 10b + c
Second number is a+ 10b + 100c
Difference is 99( a-c)
By use of divisibility rules or by exhaustion the 99 times table (1..8) has the property that the outside digits add to 9 and the middle digit is 9
So we have a number of the form 100d+ 90 + f
Add to the digits reversed d +90 + 100f
to get 101(d+f) + 180
And since d + f = 9
The result = 909+ 180 = 1089
Note that this breaks down if a= c e.g. 414 reversed is 414 the difference is zero and digit reversal sum is also zero
The usually stated condition is that the initial three digits are different.
a sufficient but not necessary condition.
Eg. 441 -144 = 297 =99*3 etc.