Asked by Biscuit
In how many whole numbers between 100 and 999 is the middle digit equal to the sum of the other two digits?
Answers
Answered by
Steve
45
Here's why:
If first digit is k, middle is k+i, last is i.
Max k+i is 9, so i ranges from 0 to 9-k
So, there are
9 numbers starting with 1,
8 starting with 2,
...
1 starting with 9
sum of numbers from 1 to 9 is 9*10/2 = 45
Here's why:
If first digit is k, middle is k+i, last is i.
Max k+i is 9, so i ranges from 0 to 9-k
So, there are
9 numbers starting with 1,
8 starting with 2,
...
1 starting with 9
sum of numbers from 1 to 9 is 9*10/2 = 45
Answered by
Anonymous
45
Answered by
ALEX
I LOVE MATHS 5+5=10
Answered by
Alice
45
Answered by
Ransa
How many whole numbers between 100 and 999 have their digits in strictly decreasing order
Answered by
Nick
198
Answered by
anon.
53. Easy.
Answered by
Reeet
ZXedv3c1 niol8
Answered by
Oscar
45 btw do u like Olivia Rodrigo?
There are no AI answers yet. The ability to request AI answers is coming soon!
Submit Your Answer
We prioritize human answers over AI answers.
If you are human, and you can answer this question, please submit your answer.