An algebra problem by Kevin Li

Algebra Level 2

If x, y, and z are positive integers and 4x=5y=9z, then what is the least possible value of x+y+z?


The answer is 101.

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5 solutions

Kevin Li
Dec 23, 2014

We will first call n. n=4x=5y=9z To find the least possible value, we must find the least possible value of n, which is the least common multiple of 4, 5, and 9, which is 180. Therefore, we get 180=4x=5y=9z. Therefore, x=45, y=36, and z=20. 45+36+20=101 Therefore, the least possible value of x+y+z is 101.

@Kevin Li I also did by the same method. 👍

Anuj Shikarkhane - 6 years, 5 months ago
William Isoroku
Dec 27, 2014

The L C D LCD of 4 , 5 , 9 4,5,9 is 180 180 . Just divide 180 180 by the the three numbers to get x , y , z x,y,z and add them.

4 x = 5 y = 9 z 4x=5y=9z

x, y, and z are positive integers.

⟹ x = 45 , y = 36 , z = 20 \implies x=45,y=36,z=20

⟹ x + y + z = 101 \implies x+y+z=\boxed{101}

Melvin Alas-as
Dec 28, 2014

If 4x=5y=9z we must find the smallest possible number divisible by 4,5&9

LCM(4,5,9)=180

180=4x=5y=9z. So (x,y,z)=(45,36,20)

x+y+z=101

Anweshan Bor
Dec 28, 2014

To get the minimum values of x, y, and z, we need to find the LCM of 4, 5 and 9. Now LCM of 4, 5 and 9 is 180 Therefore x= 180÷4=45 y= 180÷5=36 And. z=180÷9=20 Therefore minimum sum of x, y and z is 101.

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