Answer:
1134
Step-by-step explanation:
We have 3 digits:
a, b, c
a 3 digit number can be written as:
a*100 + b*10 + c*1
Such that these numbers can be:
{1, 2, 3, 4, 5, 6, 7, 8, 9}
Let's assume that:
a < b < c
Then the 3 smaller numbers are:
a*100 + b*10 + c
a*100 + c*10 + b
b*100 + a*10 + c
The 3 larger numbers are:
b*100 + c*10 + a
c*100 + a*10 + b
c*100 + b*10 + a
We know that the sum of the 3 smaller numbers is equal to 540, then:
(a*100 + b*10 + c) + (a*100 + c*10 + b) + (b*100 + a*10 + c) = 540
Let's simplify this:
(a + a + b)*100 + (b + c + a)*10 + (c + b + c) = 540
(2a + b)*100 + (b + c + a)*10 + (2c + b) = 540
The sum of the 3 larger numbers is equal to X, we want to find the value of X:
(b*100 + c*10 + a) + (c*100 + a*10 + b) + (c*100 + b*10 + a) = X
Now let's simplify the left side:
(b + c + c)*100 + (c + a + b)*10 + (a + b + a)*1 = X
(b + 2*c)*100 + (c + a + b)*10 + (2a + b) = X
Then we have two equations:
(2a + b)*100 + (b + c + a)*10 + (2c + b) = 540
(b + 2*c)*100 + (c + a + b)*10 + (2a + b) = X
Notice that the terms are inverted.
By looking at the first equation, we can see that:
(2c + b) = 10 (because the units digit of 540 is 0)
Then, we can see that:
(b + c + a + 1 ) = 14 (the one comes from the previous 10)
finally:
(2a + b + 1) = 5 (the one comes from the previous 14)
Then we can rewrite:
(2*c + b) = 10
(b + c + a) = 14 -1 = 13
(2a + b) = 5 - 1 = 4
Now we can replace these 3 in the equation:
(b + 2*c)*100 + (c + a + b)*10 + (2a + b) = X
(10)*100 + (13)*10 + 4 = X
1000 + 130 + 4 = X
1134 = X
The sum of the 3 largest numbers is 1134.
