Easy Numbers

The product N of three positive integers is 9 times their sum, and one of the integers is the sum of the other two. Find the sum of all possible values of N.


The answer is 702.

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3 solutions

Satyen Nabar
Mar 19, 2014

Let the three integers be a, b, c.

N = abc = 9(a + b + c) and c = a + b.

N = ab(a + b) = 9(a + b + a + b) = 18 (a + b).

Since a and b are positive, ab = 18 so {a, b} is one of ( 1,18) (2, 9) (3, 6).

c= a+b is one of 19, 11, 9.

N is one of 342, 198, 162.

Sum of all values is 702.

Even though at first i thought i couldn't ...........I did it the same way :)

Arya Samanta - 7 years, 2 months ago

You are really brilliant!!!

Ashley Shamidha - 7 years, 1 month ago

Solution is good but please use latex

mietantei conan - 7 years, 2 months ago

Log in to reply

Plz teach me how to use latex and what is it ?

Rohitas Bansal - 7 years, 2 months ago

i missed the value 19 and did not consider 18 and 1

akash deep - 7 years, 1 month ago
Ra Di
Mar 23, 2014

A=B+C

ABC = 9(A+B+C)

(B+C)BC = 9(B+C+B+C)

(B+C)BC = 9(2B+2C)

(B+C)BC = 9 x 2(B+C)

(B+C)BC = 18(B+C)

BC = 18

(A,B,C) = (19,1,18) OR (11,9,2) OR (9,3,6)

THE ANSWER IS SUM OF N = (19 x 1 x 8) + (11 x 9 x 2) + (9 x 3 x 6) = 342 + 198 +162

= 702

Sagnik Ghosh
Mar 30, 2014

simple trial and error program in java......the output will provide many similar values......avoid others and take one value at once........my for loop's limit is till 1000 coz brilliant.org doesn't support values after 999 ............HERE'S the PROGRAM:-

class number { void main() { for(int i=0;i<=1000;i++) { for(int j=0;j<=1000;j++) { for(int k=0;k<=1000;k++) { int sum=i+j+k; int product=i j k; if((i==j+k)||(j==i+k)||(k==i+j)) { if(product==9*sum) System.out.println(product); } } } } } }

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